<![CDATA[Purpose – This study aimed to develop and evaluate an environmental education toolkit, consisting of a student guidebook and a supporting educational video, as a strategy to enhance sustainable environmental awareness among senior high school students.Methodology – The research employed a Research and Development (R&D) design following the ADDIE model (Analysis, Design, Development, Implementation, and Evaluation) with a mixed-methods approach. The research subjects were 45 tenth-grade students of SMA Negeri 1 Dolok Silau, yielding N = 45 for the paired pretest-posttest comparisons. Data were collected through observation, questionnaires, tests, interviews, and documentation, and analyzed using the paired-samples t-test and the normalized gain (N-Gain) formula.Findings – The needs analysis revealed that the school environment was not yet optimally organized and that students' environmental awareness had not developed independently, despite a fairly high level of readiness within the school community (88.2%). Validation by material, media, and education experts yielded average feasibility scores of 92.9%, 94.4%, and 94.2%, respectively, while the research instruments were rated 96%, giving an overall feasibility of 94.4% (very feasible). Paired-samples t-tests showed significant increases in both cognitive knowledge (62.89 to 85.04; t = 10.694, df = 44, p < 0.001) and environmental awareness (77.55% to 89.88%; t = 10.441, df = 44, p < 0.001), with moderate N-Gain scores of 0.550 and 0.529, respectively. Behavioral observation indicated a steady increase in pro-environmental participation from 52.50% to 96.88% across the implementation sessions.Contribution – These findings indicate that the developed toolkit is valid, practical, and effective in fostering students' cognitive, affective, and behavioral environmental awareness, offering a replicable model for contextual environmental education in secondary schools.]]>
