Effectiveness of an Interactive Digital Intervention Program on Knowledge, Health Literacy, and Learner Engagement in Senior High School Students: Intragroup and Intergroup Comparison of 2 Teaching Models

Background: Adolescent substance use remains a critical and persistent public health concern worldwide. The initiation of drug use during adolescence is often associated with long-term negative health, social, and academic outcomes. As structured environments where young people spend a large portion of their time, schools are in a unique position to implement early prevention strategies to effectively address this issue. In recent years, digital technologies have emerged as promising tools for delivering health education in engaging and scalable ways. Objective: This study aimed to develop and evaluate an interactive digital intervention (IDI) program designed to improve high school students’ knowledge related to illegal drugs, enhance their health literacy, and promote greater learner engagement. Specifically, the study sought to compare the outcomes of a digital teaching model with those of traditional textbook-based instruction. Methods: A quasi-experimental, pre-post design was adopted involving 768 senior high school students aged between 16 and 18 years from 9 randomly selected schools. The schools were assigned to either the IDI group (n=379, 49.3%) or the traditional didactic (TD) group (n=389, 50.7%). The IDI group received a 6-unit web-based substance use prevention program with interactive features such as videos, quizzes, and scenario-based discussions. The TD group received conventional classroom instruction using standard textbooks. After accounting for student attrition and absences, 651 students remained for final analysis (IDI: n=305, 46.9%; TD: n=346, 53.1%). Paired t tests and generalized estimating equations (GEEs) were used to assess within- and between-group differences, adjusting for age and gender. Results: An intragroup comparison revealed that the IDI group had significantly greater improvements in the following variables: knowledge (t₃₀₄=–5.23, P<.01), health literacy (t₃₀₄=–3.18, P<.01), functional literacy (t₃₀₄=–3.50, P<.01), critical literacy (t₃₀₄=–2.79, P=.01), communicative literacy (t₃₀₄=–2.26, P=.02), and learner engagement (t₃₀₄=–3.40, P<.01), including cognitive engagement (t₃₀₄=–2.20, P=.03) and emotional engagement (t₃₀₄=–3.84, P<.01). While most results were consistent across paired t test and GEE analyses, cognitive engagement did not show significant intergroup differences. Conclusions: Our findings support the potential of IDIs for improving knowledge, health literacy, and engagement among high school students. Compared to traditional instruction, digital programs may provide a more engaging and impactful method for substance use prevention in educational settings. However, the intervention did not significantly improve all targeted outcomes, such as refusal skills and perceived harmfulness, suggesting the need for refined targeting and longer implementation periods. Further studies may explore the long-term behavioral outcomes and the scalability of such interventions.