The bystander readiness to help scale was based on the denial subscale of the readiness to help scale (D-RHS; Banyard et al., 2014) to assess students's awareness of and willingness to engage in prevention efforts regarding CSE among high school students in their school district. These items have similarly been adapted for measuring opinions regarding relationship abuse and/or sexual assault among high school students (Edwards et al., 2018). The scale consists of four statements using a 4-point Likert scale (1 = strongly agree to 4 = strongly disagree). A total score is calculated from the average of the items, with higher scores reflective of a greater sense of need and the willingness to engage.

Behaviorally worded items to assess students' self-reports of experiencing past month sexual assault victimization, with items adapted from Cook-Craig et al. (2014). The scale consists of 4 items with response options (1=Yes, 0=No, and -999=I don't want to answer). The original scale has response options ranging from 0-4 (0=0 times, 4=10+ times). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-4. Higher scores indicate more instances of sexual assault victimization having occurred.

Behaviorally worded items to assess students' self-reports of experiencing past month sexual assault perpetration, with items adapted from Cook-Craig et al. (2014). The scale consists of 4 items with response options (1=Yes, 0=No, and -999=I don't want to answer). The original scale has response options ranging from 0-4 (0=0 times, 4=10+ times). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-4. Higher scores indicate more instances of sexual assault perpetration having occurred.

Behaviorally worded items to assess past month students' self-reports of experiencing sexual harassment victimization. Items adapted from American Association of University Women Educational Foundation (2001, p.21). The scale consists of 2 items with response options (1=Yes, 0=No, and -999=I don't want to answer). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-2. Higher scores indicate more instances of sexual harrassment victimization having occurred.

Behaviorally worded items to assess past month students' self-reports of experiencing sexual harassment perpetration. Items adapted from American Association of University Women Educational Foundation (2001, p.21). The scale consists of 2 items with response options (1=Yes, 0=No, and -999=I don't want to answer). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-2. Higher scores indicate more instances of sexual harrassment perpetration having occurred.

Behaviorally worded items to assess students' past month self-reports of experiencing stalking victimization, with items adapted from(Cook-Craig et al. 2014). The scale consists of 3 items with response options (1=Yes, 0=No, and -999=I don't want to answer). The original scale has response options ranging from 0-4 (0=0 times, 4=10+ times). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-3. Higher scores indicate more instances of stalking victimization having occurred.

Behaviorally worded items to assess students' past month self-reports of experiencing stalking perpetration, with items adapted from(Cook-Craig et al. 2014). The scale consists of 3 items with response options (1=Yes, 0=No, and -999=I don't want to answer). The original scale has response options ranging from 0-4 (0=0 times, 4=10+ times). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-3. Higher scores indicate more instances of stalking perpetration having occurred.

The Measure of Adolescent Relationship Harassment and Abuse (MARSHA; Rothman et al. 2020) was used to assess past month dating violence victimization. The scale consists of two subscales, Physical abuse (7 items) and Isolation (3 items), with response options of 1=Yes, 0=No, and -999=I don't want to answer. A total score is calculated from the counting the nunber of items answers as "yes". Higher scores indicate more instances of dating violence victimization having occurred.

The Measure of Adolescent Relationship Harassment and Abuse (MARSHA; Rothman et al. 2020) was used to assess past month dating violence perpetration. The scale consists of two subscales, Physical abuse (7 items) and Isolation (3 items), with response options of 1=Yes, 0=No, and -999=I don't want to answer. A total score is calculated from the counting the nunber of items answers as "yes". Higher scores indicate more instances of dating violence perpetration having occurred.

The Youth Risk Behavior Surveillance System (YRBS; Centers for Disease Control and Prevention, 2019) was used to measure past month physical fights, fear of going to school, and weapon carrying. The scale consisted of 4 items with response options of 1=Yes, 0=No, and -999=I don't want to answer. A total score is calculated from the counting the nunber of items answers as "yes". Higher scores indicate more instances of youth violence having occurred.

The Patient Health Questionnaire (PHQ-9) modified (Johnson et al. 2002) was used to measure past two week depression. The scale consisted of 8 items with response options from Not at all (0) to Nearly every day (3) and I don't want to answer (-999). The toal score is calculated from the average of the items, with higher scores representing higher depression symptoms.

Items from Hulsey et al. (2022) were used to measures students intentions on graduating high school/getting a GED as well as having a job/career. The scale consisted of 5 items with response scales from Not at all true of me (1) to Extremely true of me (4) and I don't want to answer this question (-999). The total scores were calculated from the average of the items, with higher scores representing higher academic and career commitment.

Author created items to assess confidence in resistance to being a victim of CSEC. Two statements asked how confident the participant is in recognizing sex trafficking (i.e., "If someone tried to force you into sex trafficking, how confident are you that you would recognize it?"), and keeping it from happening (i.e., "If someone tried to force you into sex trafficking, how confident are you that you would be able to keep it from happening?"). Participants rated the statements using the four options: Not at all confident (1), Somewhat confident (2), Very confident (3) , and I don't want to answer this question (-999). Total score was calculated into a mean with higher scores indicating higher efficacy.

The Valuing of Self (e.g., "I have value") scales was adapted from measures and conceptualizations of positive youth development (PYD; Bowers et al., 2010; Lerner et al., 2005; Park, 2010) and dignity scales (Bal, 2017; Lebech, 2004; Ziebertz et al., 2018). Prior to the questions, a definition of value was provided. The scale included eight statements. Participants rated statements from strongly disagree (1) to strongly agree (4). Scores were calculated by taking the average of the items with higher scores indicating higher sense of valuing of self.

The Valuing of Others (e.g., "All people have value") scale was adapted from measures and conceptualizations of positive youth development (PYD; Bowers et al., 2010; Lerner et al., 2005; Park, 2010) and dignity scales (Bal, 2017; Lebech, 2004; Ziebertz et al., 2018). Prior to the questions, a definition of value was provided. The scale included eight statements. Participants rated statements from strongly disagree (1) to strongly agree (4). Scores were calculated by taking the average of the items with higher scores indicating higher sense of valuing of other.

The Social Norms scale (Waterman et al., 2022) (adapted from prior work; Waterman et al., 2022) is composed of four subscales that gauges personal beliefs, perceptions of friends, perceptions of other high school students in this district, and perceptions of school personnel in the district regarding their beliefs on sex trafficking. Participants rated all statements on a scale from strongly disagree (1) to strongly agree (4). An option of I don't want to answer was also provided. Subscale scores were calculated from the average of the items, with higher scores representing social norms less supporting of sex trafficking, including personal beliefs, perceptions of friends, other high school students, and school personnel.

We adapted items created by Edwards et al. (2021, 2022). The eight statements focused on things school personnel had discussed with students, including general items such as how to have healthy relationships and their futures, as well as CSE items, including sex trafficking, sexual assault, and dating and/or domestic violence, and to what extent they agreed with each statement (1 = strongly disagree to 4 = strongly agree). The final score was the average of the scale items, with higher values indicating more engagement between students and school personnel.

Consistent with other measures of sexual violence/teen dating violence knowledge for youth (Edwards et al., 2019), questions (e.g., "most victims are trafficked by strangers") are True/False. We provide youth a definition of CSE, specifically, sex trafficking. We created nine items to assess school personnel's general knowledge about CSE and the roles school personnel can play in its prevention. The respondents are asked if they believe the statements to be true or false. Items are scored based upon whether they were answered correctly (1) or incorrectly (0). The scores were then averaged to create a cumulative score that reflects the proportion of statements answered correctly

The bystander readiness to help scale was based on the denial subscale of the readiness to help scale (D-RHS; Banyard et al., 2014b) to assess school personnel's awareness of and willingness to engage in prevention efforts regarding CSE among high school students in their school district. These items have similarly been adapted for measuring opinions regarding relationship abuse and/or sexual assault among high school students (Edwards et al., 2018). The scale consists of four statements using a 4-point Likert scale (1 = strongly agree to 4 = strongly disagree). A total score is calculated from the average of the items, with higher scores reflective of a greater sense of need and the willingness to engage.

The Social Norms scale (Waterman et al., 2022) (adapted from prior work; Waterman et al., 2022) is composed of four subscales that gauges personal beliefs, perceptions of friends, perceptions of other high school students in this district, and perceptions of school personnel in the district regarding their beliefs on sex trafficking. For school personnels, three out of the four subscales were included (i.e., personal belief, perceptions of high school students in this district, and perceptions of school personnel in the district). Participants rated all statements on a scale from strongly disagree (1) to strongly agree (4). An option of I don't want to answer was also provided. Subscale scores were calculated from the average of the items, with higher scores representing social norms less supporting of sex trafficking, including personal beliefs, other high school students, and school personnel.

We adapted items created by Edwards et al. (2021, 2022). The eight statements focused on things school personnel had discussed with students, including general items such as how to have healthy relationships and their futures, as well as CSE items, including sex trafficking, sexual assault, and dating and/or domestic violence, and to what extent they agreed with each statement (1 = strongly disagree to 4 = strongly agree). The final score was the average of the scale items, with higher values indicating more engagement between students and school personnel.

The Cultural Humility scale was based on The Multicultural Teaching Competency Scales (Spanierman et al., 2011). The scale consists of 16 statements using a 5-point Likert scale (1 = strongly disagree to 5 =strongly agree). The total score is calculated from the average of the items, with higher scores reflective of a higher sense of cultural humility.

RTS intervention will include six, 45-minute sessions (total = 4.5 hours) for students. There are five components in this intervention that students will receive: 1) Psychoeducation on CSEC, 2) Healthy relationship skills training, 3) Programming components to enhance valuing of self and others, 4) Bystander intervention skills, and 5) Social norms for both students and school personnel. Students will additionally receive programming on Identification of safe people and resources, while school personnel will receive programming on Responding to Student Disclosures, and Cultural Humility.

READY To Stand Curriculum: Students will receive the RTS programming over six consecutive school days, spread over two weeks. The program is delivered in mixed-gender groups of 20 to 40 students and includes videos, small and large group discussions, activities, worksheets, and ample opportunities for skill-building. This curriculum is intended to be one piece of comprehensive prevention strategies that has the potential to make immediate and sustained impacts on reducing rates of CSEC perpetration in the lives of youth, including those most vulnerable to this pernicious crime.

Total of all reporting groups

Row population differs from overall due to missing values. RTS Intervention - Student group didn't have the option for "Other" as a gender

For the initial pool of items, we identified existing CSEC victimization items from The National Study on Adolescent to Adult Health (ADD Health; Franchino-Olsen et al., 2021) and The My Life My Choices evaluation study (Rothman et al., 2021). The scale consists of 21 statements and response options included yes, no, or I do not want to answer this question. A total score is calculated from the sum of the items, with higher scores reflective of a higher sex trafficking victimization experiences in the past month.

Students from two public Midwestern high schools (one traditional and one alternative)

The bystander readiness to help scale was based on the denial subscale of the readiness to help scale (D-RHS; Banyard et al., 2014) to assess students's awareness of and willingness to engage in prevention efforts regarding CSE among high school students in their school district. These items have similarly been adapted for measuring opinions regarding relationship abuse and/or sexual assault among high school students (Edwards et al., 2018). The scale consists of four statements using a 4-point Likert scale (1 = strongly agree to 4 = strongly disagree). A total score is calculated from the average of the items, with higher scores reflective of a greater sense of need and the willingness to engage.

Students from two public Midwestern high schools (one traditional and one alternative)

Behaviorally worded items to assess students' self-reports of experiencing past month sexual assault victimization, with items adapted from Cook-Craig et al. (2014). The scale consists of 4 items with response options (1=Yes, 0=No, and -999=I don't want to answer). The original scale has response options ranging from 0-4 (0=0 times, 4=10+ times). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-4. Higher scores indicate more instances of sexual assault victimization having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

Behaviorally worded items to assess students' self-reports of experiencing past month sexual assault perpetration, with items adapted from Cook-Craig et al. (2014). The scale consists of 4 items with response options (1=Yes, 0=No, and -999=I don't want to answer). The original scale has response options ranging from 0-4 (0=0 times, 4=10+ times). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-4. Higher scores indicate more instances of sexual assault perpetration having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

Behaviorally worded items to assess past month students' self-reports of experiencing sexual harassment victimization. Items adapted from American Association of University Women Educational Foundation (2001, p.21). The scale consists of 2 items with response options (1=Yes, 0=No, and -999=I don't want to answer). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-2. Higher scores indicate more instances of sexual harrassment victimization having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

Behaviorally worded items to assess past month students' self-reports of experiencing sexual harassment perpetration. Items adapted from American Association of University Women Educational Foundation (2001, p.21). The scale consists of 2 items with response options (1=Yes, 0=No, and -999=I don't want to answer). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-2. Higher scores indicate more instances of sexual harrassment perpetration having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

Behaviorally worded items to assess students' past month self-reports of experiencing stalking victimization, with items adapted from(Cook-Craig et al. 2014). The scale consists of 3 items with response options (1=Yes, 0=No, and -999=I don't want to answer). The original scale has response options ranging from 0-4 (0=0 times, 4=10+ times). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-3. Higher scores indicate more instances of stalking victimization having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

Behaviorally worded items to assess students' past month self-reports of experiencing stalking perpetration, with items adapted from(Cook-Craig et al. 2014). The scale consists of 3 items with response options (1=Yes, 0=No, and -999=I don't want to answer). The original scale has response options ranging from 0-4 (0=0 times, 4=10+ times). A total score is calculated from taking a count of items with a response of "yes", with scores ranging from 0-3. Higher scores indicate more instances of stalking perpetration having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

The Measure of Adolescent Relationship Harassment and Abuse (MARSHA; Rothman et al. 2020) was used to assess past month dating violence victimization. The scale consists of two subscales, Physical abuse (7 items) and Isolation (3 items), with response options of 1=Yes, 0=No, and -999=I don't want to answer. A total score is calculated from the counting the nunber of items answers as "yes". Higher scores indicate more instances of dating violence victimization having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

The Measure of Adolescent Relationship Harassment and Abuse (MARSHA; Rothman et al. 2020) was used to assess past month dating violence perpetration. The scale consists of two subscales, Physical abuse (7 items) and Isolation (3 items), with response options of 1=Yes, 0=No, and -999=I don't want to answer. A total score is calculated from the counting the nunber of items answers as "yes". Higher scores indicate more instances of dating violence perpetration having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

The Youth Risk Behavior Surveillance System (YRBS; Centers for Disease Control and Prevention, 2019) was used to measure past month physical fights, fear of going to school, and weapon carrying. The scale consisted of 4 items with response options of 1=Yes, 0=No, and -999=I don't want to answer. A total score is calculated from the counting the nunber of items answers as "yes". Higher scores indicate more instances of youth violence having occurred.

Students from two public Midwestern high schools (one traditional and one alternative)

The Patient Health Questionnaire (PHQ-9) modified (Johnson et al. 2002) was used to measure past two week depression. The scale consisted of 8 items with response options from Not at all (0) to Nearly every day (3) and I don't want to answer (-999). The toal score is calculated from the average of the items, with higher scores representing higher depression symptoms.

Students from two public Midwestern high schools (one traditional and one alternative)

Items from Hulsey et al. (2022) were used to measures students intentions on graduating high school/getting a GED as well as having a job/career. The scale consisted of 5 items with response scales from Not at all true of me (1) to Extremely true of me (4) and I don't want to answer this question (-999). The total scores were calculated from the average of the items, with higher scores representing higher academic and career commitment.

Students from two public Midwestern high schools (one traditional and one alternative)

Consistent with other measures of sexual violence/teen dating violence knowledge for youth (Edwards et al., 2019), questions (e.g., "most victims are trafficked by strangers") are True/False. We provide youth a definition of CSE, specifically, sex trafficking. We created six items to measure adolescents' knowledge of CSE. The respondents are asked if they believe the statements to be true or false. Items are scored based upon whether they were answered correctly (1) or incorrectly (0). The scores were then averaged to create a cumulative score that reflects the proportion of statements answered correctly (Min=0, Max=6).

Author created items to assess confidence in resistance to being a victim of CSEC. Two statements asked how confident the participant is in recognizing sex trafficking (i.e., "If someone tried to force you into sex trafficking, how confident are you that you would recognize it?"), and keeping it from happening (i.e., "If someone tried to force you into sex trafficking, how confident are you that you would be able to keep it from happening?"). Participants rated the statements using the four options: Not at all confident (1), Somewhat confident (2), Very confident (3) , and I don't want to answer this question (-999). Total score was calculated into a mean with higher scores indicating higher efficacy.

Students from two public Midwestern high schools (one traditional and one alternative)

The Valuing of Self (e.g., "I have value") scales was adapted from measures and conceptualizations of positive youth development (PYD; Bowers et al., 2010; Lerner et al., 2005; Park, 2010) and dignity scales (Bal, 2017; Lebech, 2004; Ziebertz et al., 2018). Prior to the questions, a definition of value was provided. The scale included eight statements. Participants rated statements from strongly disagree (1) to strongly agree (4). Scores were calculated by taking the average of the items with higher scores indicating higher sense of valuing of self.

Students from two public Midwestern high schools (one traditional and one alternative)

The Valuing of Others (e.g., "All people have value") scale was adapted from measures and conceptualizations of positive youth development (PYD; Bowers et al., 2010; Lerner et al., 2005; Park, 2010) and dignity scales (Bal, 2017; Lebech, 2004; Ziebertz et al., 2018). Prior to the questions, a definition of value was provided. The scale included eight statements. Participants rated statements from strongly disagree (1) to strongly agree (4). Scores were calculated by taking the average of the items with higher scores indicating higher sense of valuing of other.

Students from two public Midwestern high schools (one traditional and one alternative)

The Social Norms scale (Waterman et al., 2022) (adapted from prior work; Waterman et al., 2022) is composed of four subscales that gauges personal beliefs, perceptions of friends, perceptions of other high school students in this district, and perceptions of school personnel in the district regarding their beliefs on sex trafficking. Participants rated all statements on a scale from strongly disagree (1) to strongly agree (4). An option of I don't want to answer was also provided. Subscale scores were calculated from the average of the items, with higher scores representing social norms less supporting of sex trafficking, including personal beliefs, perceptions of friends, other high school students, and school personnel.

Students from two public Midwestern high schools (one traditional and one alternative)

We adapted items created by Edwards et al. (2021, 2022). The eight statements focused on things school personnel had discussed with students, including general items such as how to have healthy relationships and their futures, as well as CSE items, including sex trafficking, sexual assault, and dating and/or domestic violence, and to what extent they agreed with each statement (1 = strongly disagree to 4 = strongly agree). The final score was the average of the scale items, with higher values indicating more engagement between students and school personnel.

Students from two public Midwestern high schools (one traditional and one alternative)

Consistent with other measures of sexual violence/teen dating violence knowledge for youth (Edwards et al., 2019), questions (e.g., "most victims are trafficked by strangers") are True/False. We provide youth a definition of CSE, specifically, sex trafficking. We created nine items to assess school personnel's general knowledge about CSE and the roles school personnel can play in its prevention. The respondents are asked if they believe the statements to be true or false. Items are scored based upon whether they were answered correctly (1) or incorrectly (0). The scores were then averaged to create a cumulative score that reflects the proportion of statements answered correctly

School Personnel from all high schools within the district

The bystander readiness to help scale was based on the denial subscale of the readiness to help scale (D-RHS; Banyard et al., 2014b) to assess school personnel's awareness of and willingness to engage in prevention efforts regarding CSE among high school students in their school district. These items have similarly been adapted for measuring opinions regarding relationship abuse and/or sexual assault among high school students (Edwards et al., 2018). The scale consists of four statements using a 4-point Likert scale (1 = strongly agree to 4 = strongly disagree). A total score is calculated from the average of the items, with higher scores reflective of a greater sense of need and the willingness to engage.

School Personnel from all high schools within the district

The Social Norms scale (Waterman et al., 2022) (adapted from prior work; Waterman et al., 2022) is composed of four subscales that gauges personal beliefs, perceptions of friends, perceptions of other high school students in this district, and perceptions of school personnel in the district regarding their beliefs on sex trafficking. For school personnels, three out of the four subscales were included (i.e., personal belief, perceptions of high school students in this district, and perceptions of school personnel in the district). Participants rated all statements on a scale from strongly disagree (1) to strongly agree (4). An option of I don't want to answer was also provided. Subscale scores were calculated from the average of the items, with higher scores representing social norms less supporting of sex trafficking, including personal beliefs, other high school students, and school personnel.

School Personnel from all high schools within the district

We adapted items created by Edwards et al. (2021, 2022). The eight statements focused on things school personnel had discussed with students, including general items such as how to have healthy relationships and their futures, as well as CSE items, including sex trafficking, sexual assault, and dating and/or domestic violence, and to what extent they agreed with each statement (1 = strongly disagree to 4 = strongly agree). The final score was the average of the scale items, with higher values indicating more engagement between students and school personnel.

School Personnel from all high schools within the district

The Cultural Humility scale was based on The Multicultural Teaching Competency Scales (Spanierman et al., 2011). The scale consists of 16 statements using a 5-point Likert scale (1 = strongly disagree to 5 =strongly agree). The total score is calculated from the average of the items, with higher scores reflective of a higher sense of cultural humility.

School Personnel from all high schools within the district

RTS intervention will include six, 45-minute sessions (total = 4.5 hours) for students. There are five components in this intervention that students will receive: 1) Psychoeducation on CSEC, 2) Healthy relationship skills training, 3) Programming components to enhance valuing of self and others, 4) Bystander intervention skills, and 5) Social norms for both students and school personnel. Students will additionally receive programming on Identification of safe people and resources, while school personnel will receive programming on Responding to Student Disclosures, and Cultural Humility.

READY To Stand Curriculum: Students will receive the RTS programming over six consecutive school days, spread over two weeks. The program is delivered in mixed-gender groups of 20 to 40 students and includes videos, small and large group discussions, activities, worksheets, and ample opportunities for skill-building. This curriculum is intended to be one piece of comprehensive prevention strategies that has the potential to make immediate and sustained impacts on reducing rates of CSEC perpetration in the lives of youth, including those most vulnerable to this pernicious crime.

Staff members were recruiting participants and conducting outreach visits in the community going door-to-door using a door knocking protocol that had not yet been approved in this study but had been previously used in other studies.