Musculoskeletal pain during childhood can negatively affect school attendance, physical activity, and social participation. This study will evaluate the effectiveness of the school-based health education program 'SocLaLola', which uses a comic-based narrative to introduce children to pain science concepts and promote healthy lifestyle habits. The intervention will be compared with a standard program focused on sedentary behavior prevention. Students aged 8 to 11 years from two primary schools will participate. The primary objective is to determine whether SocLaLola is more effective than the comparison program in improving children's knowledge about pain and in reducing fear-avoidance beliefs related to physical activity.

This randomized controlled trial will evaluate the effectiveness of the 'SocLaLola' school-based health education program compared with a sedentary lifestyle prevention program in modifying pain-related beliefs and knowledge among children aged 8 to 11 years. The primary outcomes are improvements in pain science knowledge and reductions in fear-avoidance beliefs toward physical activity.

Participants will be recruited from schools participating in the Catalan Board of Physiotherapists' School Health Program. Two primary schools will take part, each contributing two fourth-grade classes. Randomization will be performed at the class level, with classes within each school allocated to either the intervention group (SocLaLola Program) or the control group (Stop Sedentarism Program) using an online random assignment tool. This procedure ensured blocked randomization by school.

Both interventions will be delivered by trained physiotherapists in a single 45-60 minute session. The SocLaLola program combines pain science education with strategies to reduce sedentary behavior, presented through a comic-based narrative. The control group will receive audiovisual materials focusing exclusively on sedentary behavior.

Assessments will be conducted at baseline, immediately after the session, and at six months. Data collection and analysis will follow a single-blind design. Ethical approval for the study was obtained from the Research Ethics Committee of the Catalan Board of Physiotherapists (CER CFC).

Inclusion criteria:

• Boys and girls from 8 to 11 years old.
• Attend the 3rd or 4th grade of primary education.
• Students from selected schools participating in the CFC project.
• Their parents or legal guardians have signed the informed consent

Exclusion criteria:

• Does not meet one or more inclusion criteria.
• Does not demonstrate reading comprehension in Catalan or Spanish.
• Does not wish to participate.

Individual participant data (IPD) underlying the results reported in this trial will be shared in de-identified form. Specifically, the datasets will include socio-demographic variables (age, sex, school, cohabitant pain history), responses to the Fear-Avoidance Beliefs Questionnaire (FABQ-PA), responses to the Conceptualization of Pain Questionnaire (COPAQ), and answers to the open-ended post-intervention question. All data will be pseudonymized with unique alphanumeric codes, ensuring that no personally identifiable information will be disclosed. Study protocol, statistical analysis plan, and informed consent templates will also be made available to support secondary analyses. Access to the data will require a justified request and approval by the principal investigator, and data will be shared through secure institutional repositories in accordance with ethical guidelines and data protection regulations (GDPR).

De-identified IPD and supporting documents (Study Protocol, SAP, ICF) will be available beginning 12 months after publication of the primary results and will remain accessible for a period of 5 years through secure institutional repositories, upon reasonable request and approval by the principal investigator.

De-identified individual participant data (IPD) and supporting documents (Study Protocol, Statistical Analysis Plan, and Informed Consent Form) will be accessible to qualified researchers affiliated with academic institutions or health research organizations, for the purpose of scientific research related to pain science education, musculoskeletal health, or school-based interventions. Access will be granted upon submission of a justified research proposal, review and approval by the principal investigator, and signature of a data access agreement. Data will be shared through secure institutional repositories in accordance with ethical standards and data protection regulations (GDPR).

Due to the educational nature of the intervention, it was not possible to blind participants or the physiotherapists delivering the sessions, as they were aware of the content assigned to their group. However, several procedures were implemented to ensure single-blind conditions and minimize potential bias:

• The same physiotherapist delivered the educational sessions for both the intervention and control groups, ensuring consistency in delivery style.
• A different member of the research team was responsible for distributing and collecting the evaluation questionnaires, reducing direct interaction between the educator and the assessment process.
• Data analysis was conducted by an evaluator blinded to group allocation.
• Only the principal investigator had access to the encrypted list linking participant codes to personal identifiers.
• All questionnaires and records were pseudonymized using unique alphanumeric codes to preserve confidentiality and ensure data protection.