Background: Although it is widely recognized that more attention needs to be paid to children's fluid intake, there is little information on how to improve it. Peer education has been suggested as an effective approach to changing health behaviors among school children. As a new approach, our study piloted a peer education program to improve children's fluid intake in primary schools. Methods: University students were prepared for their role as peer educators in an elective university course, including the concept of peer education and different pedagogical methods. The peer educators evaluated the training process by completing a questionnaire. The intervention took place during a School Health Day led by the peer educators. An anonymous survey with a questionnaire on knowledge of fluid intake was administered two weeks before, at the end of, and 15 weeks after the intervention. Changes in hydration knowledge were tested using repeated measures ANOVA. Results: The pilot program showed increased knowledge about fluid consumption (p < 0.001) in lower and upper primary school children (N = 326) at the end of the School Health Day compared to pre-intervention measures. A positive change was observed after 15 weeks only in upper primary students. Feedback from peer educators was useful for fine-tuning the program. Conclusions: This innovative program induced positive changes in knowledge about fluid intake in primary school children. The persistence of the changes differed between lower and upper primary school children. Based on the results, the intervention should be replicated to adapt the program to the needs of lower primary school children. Because the training of peer educators and the peer education program appeared to be successful, this program is worthy of international replication. This approach may also be suggested for other behavior change issues.

Introduction: Marked gender differences have been identified in cyberbullying perpetration and victimization in adolescence. Age and phenotypic traits, including impulsivity and problematic internet use may mediate the association between gender and cyberbullying intervention outcomes. This study thus aimed to explore gender differences and the potential mediating role of age, impulsivity and problematic internet use regarding the outcomes of an elementary school cyberbullying program. Methods: The peer-led STAnD project shapes students' attitudes towards cyberbullying, and promotes help-seeking behaviors. Baseline sample consisted of 933 respondents (51.3% females, mean age = 11.25, sd = 1.64), and after a 42.55% drop-out, 536 remained in the sample for 6-month follow-up. Four primary outcome measures represented protective factors against cyberbullying. Results: Three of the intervention outcomes – change in 1) helpline knowledge, 2) empathy towards the victims of cyberbullying, and 3) risk perception regarding online hazards - were best predicted by gender. A gender-specific path analysis model indicated that higher amount of time spent online might put a barrier to changes in risk awareness among females and in help-seeking willingness among males. Conclusions: Future cyberbullying programs may design separate interventions for adolescent boys and girls with different emphasis placed on empathy training, or the barriers to help-seeking.