<![CDATA[Introduction: Gastritis can affect adolescents' daily functioning and may be associated with irregular eating patterns and limited knowledge of prevention. School-based health education using leaflets is a practical approach for delivering concise health information. This study evaluated changes in adolescents' knowledge of gastritis following leaflet-based health education at MTsS Serambi Mekkah, West Aceh Regency, Indonesia. Methods: A quasi-experimental one-group pretest-posttest study was conducted among 66 students. Data were collected from January 26 to 31, 2026. Participants completed a knowledge pretest, received health education supported by a leaflet, and completed a posttest. Pre- and post-intervention knowledge scores were compared using the Wilcoxon signed-rank test. Results: The mean knowledge score increased from 6.58 (SD 2.42) before the intervention to 8.56 (SD 2.53) after the intervention. The proportion of participants categorized as having poor knowledge decreased from 59.1% to 15.2%, while good knowledge increased from 12.1% to 33.3%. The Wilcoxon signed-rank test showed a statistically significant pre-post difference (Z = -5.815; p < 0.001). Conclusion: Adolescents had higher gastritis knowledge scores after leaflet-based health education. Because the study used a single-group pretest-posttest design, the findings support short-term improvement after the intervention but do not establish a definitive causal effect. Controlled studies with longer follow-up are warranted.]]>
