The goal of the current study is to examine the degree to which measures of quality of implementation and student engagement moderate pretest--posttest changes in mediating variables that are targeted by DARE "keepin' it REAL." DARE officers (10 elementary school, five middle school) taught DARE "keepin' it REAL lessons to 1,017 elementary students (480 boys and 534 girls) and 435 middle school students (217 boys and 215 girls). We examined teachers' and students' ratings of elementary and middle schools in response to DARE officers' delivery of the program. HLM analyses revealed that students' engagement was a significant and meaningful predictor of changes in targeted mediators. Teachers' ratings of student responsiveness added little in terms of understanding these outcomes with main effects observed only for students' ability to respond to bulling and students' estimates of peer drug use. Teachers' ratings of the quality of officer implementation, on the other hand, did add to understanding students' outcomes. Effects were seen for three (peer norms about drug use, decision-making (DM) skills, intentions to avoid drug use) out of six outcome variables and suggest a stronger positive effect for elementary versus middle school students. At least for these three outcomes, understanding quality of implementation added to our ability to interpret results. Specifically, in addition to students' engagement, quality of implementation (which varied by grade) contributed to achieving positive changes in students' outcomes.