The present study aimed to test the effectiveness of motivated social-emotional Learning (MSEL) and traditional curriculum-based social-emotional learning (CSEL) in reducing bullying perpetration and victimization among Hong Kong primary school students. The main research questions the cRCT aims to answer are:

1. Does MSEL reduce bullying perpetration and victimization among Hong Kong primary school students?
2. Is MSEL more effective than the traditional CSEL in reducing bullying perpetration and victimization among Hong Kong primary school students?

In according with the research questions, the following hypotheses will be tested:

H1: MSEL can significantly change primary outcomes and secondary outcomes at posttest and 3-month follow-up.

H2: CSEL can significantly change primary outcomes and secondary outcomes at posttest and 3-month follow-up.

H3: Compared with the intervention group of CSEL, the MSEL group will experience greater changes in primary and secondary outcomes.

Classroom is the randomization unit and the participating classrooms are randomly assigned to each of the three arms-the waitlist control group (WCL, no intervention delivered during the implementation period), the CSEL group (only receiving curriculum-based SEL training), and the MSEL group (participating in CSEL and Class Ambassador). The multi-method (i.e., questionnaires and face-to-face interviews) approach will be used to assess primary outcomes (i.e., school bullying victimization and perpetration, cyberbullying perpetration, defending behaviors) and secondary outcomes (i.e., social-emotional competence, prosocial behaviors, school safety and liking, psychological well-being). Also, the data collection will be conducted in the 2024-2025 academic term at three different time points: the baseline (T0, prior to the beginning of intervention, Sept. 2024), the posttest (T1, the completion of intervention, Dec. 2024) and the follow-up (T2, three months after the completion of intervention, April 2025). The analysis and report of the data start in the fall of 2025.

Informed by self-determination theory and the evolutionary theory, the intervention aims to enable primary school students in Hong Kong to enhance behavioral management and choose healthier behaviors by 1) promoting their autonomy, relatedness, and competence; and 2) achieving more social rewards through prosocial opportunities. These are theorized as being facilitated by 1) autonomy in taking pro-social responsibilities, 2) competence empowerment, and 3) interpersonal relatedness (teacher-student and peer relatedness). The intervention aims to do so via three intervention components (see intervention logic model Appendix Figure A1). First, social-emotional learning (SEL) will be delivered to students to improve students competence in five developmental domains (i.e., self-awareness, social-awareness, self-management, responsible decision-making, and relationship skills. Second, students will be offered the opportunity to autonomously take responsible and meaningful roles and to earn social benefits. Third, built on meaningful role-taking, students will recognize and connect to others by expressing compliments and by helping others in need in their own ways. The above three components will serve as both the universal and indicated approach. The universal approach aims at reducing misconduct and enhancing prosocial behaviors among all students. The indicated approach, through the use of tailored social roles and application of SEL training with specific topics (e.g., stress management, conflict solving, interpersonal skill lab), targets socially integrated bullies and socially marginalized bullies respectively.

Schools are recruited voluntarily. Based on the inclusion criteria, all eligible schools will be identified from the list of primary schools in Hong Kong, totaling 477, obtained from the Hong Kong Education Bureau. With the support of a local NGO, invitations will be sent to all qualifying middle-band schools through the nonprofit organization. In the invitation email, schools will receive information about training, implementation, and the nature of the proposed evaluation to gain their initial interest and commitment. Participation will be offered on a first-come-first-served basis to schools that respond to the invitation email and confirm their commitment, in writing, to (1) deliver the assigned intervention program and (2) participate in the evaluation. If parents or caregivers are willing to have their children participate in the CRCT, they will be required to provide informed written consent. Meanwhile, parents can request the withdrawal of their children from the trial assessments at baseline or at any other time throughout the project. Additionally, students will sign an assent to indicate their agreement or disagreement to participate in the research.

The author of the study and the registered social workers (RSW) from the collaborated agency will coach and support the intervention schools throughout the implementation. Each facilitator (headteacher from each class) will be assigned to a supervisor (RSW) to discuss the implementation. Meanwhile, five fidelity control methods will be applied in this program.

1. Programme manuals. Detailed program manuals are tailored for different intervention components in CSEL and MSEL arms. The program manual for the CSEL group includes all the details regarding the operation of the 6-session SEL curriculum. For the MSEL group, other than the program manual for SEL curriculum, the program manuals for meaningful role-taking and secret angel are also for headteachers.
2. Intervention training. Before the intervention begins, headteachers in the intervention group will be systematically trained for 2 times (2 hours each), which fully covers the operation of program manuals. First, headteachers in CSEL will be trained in delivering the SEL curriculum. Headteachers will be provided with the opportunities to go through the manual with the trainers (professional social workers from the collaborated agency) and empowered with SEL-related techniques (e.g., ROPE for SEL training rules) and skills (e.g., cultivating a safe environment for sharing) through various training setups, such as role-play, group activities and mock class.
3. SEL lesson report. Facilitators will fill out a lesson report form each time they deliver an SEL session.
4. Implementation checklist. To verify intervention fidelity, two individuals who are not members of the program will observe the implementation of all intervention components and document the concordance between a prespecified checklist of elements for the intervention and the actual implementation itself. These checklists are developed separately for each intervention component. Interrater reliability using the Kappa statistic will be computed to assess the coding reliability.
5. Biweekly and monthly meetings. Facilitators and their assigned supervisors will conduct biweekly meetings to discuss the lesson report, teaching strategies, and other contingencies. Additionally, monthly meetings will be held between the research team and supervisors to check on the implementation of the intervention and to fix problems if necessary.

• The inclusion criteria for schools, classes, and students are as follows.

  1. Primary School: To reduce the confounding effect of academic achievements on student behavior, only public schools in the middle band (i.e., the middle 33% of academic ratings) in Hong Kong will be included in the sampling. Single-sex schools will be excluded in consideration of the sampling diversity. Furthermore, schools implementing other manualized anti-bullying programs will not be included.
  2. Classes: The inclusion criteria are classes from Grade 4 and 6 (ages 9-13 years old). This research specifically targets classes in Grades 4 and 6 for several reasons. First, studying the integration of adaptive and maladaptive functions of problematic behaviors during this sensitive period may have a greater impact on young adolescents (Ellis et al., 2011). Secondly, a meta-analysis conducted by Yeager et al. (2015) reveals that the effectiveness of anti-bullying interventions declines significantly after Grade 7. Hence, the trial focuses on classes in Grades 4-6.
  3. Students: Inclusion criteria for students specify that they must be enrolled in the class and regularly attend its lessons.

• The exclusion criteria schools executing other manualized anti-bullying programs are excluded in this intervention.

Due to the nature of the RCT, blinding the trial participants, school officials, and teachers is not possible. Also, the investigator and the outcome assessor cannot be masked in the research.