A summary of important findings from the School Health Education Evaluation (SHEE) are reported. This paper focuses on the four principal outcome scores of Overall Knowledge, Attitude, Practice, and Program-Specific Knowledge. The relationship of those scores to measures of program implementation and cost also is described. A consistent pattern of findings emerged across the participating health instruction programs, suggesting that health instruction was effective in meeting program objectives as taught in the study classrooms, and that school health program effectiveness was strongly related to the level of implementation. Significant increases in Overall Knowledge and Program-Specific Knowledge were found for treatment classrooms when compared with control classrooms. Smaller, yet statistically significant, increases were found for attitudes and self-reported practices. Curriculum implementation measures were related to program effectiveness. A higher level of program implementation produced greater increases in all scores, but was most strongly related to improvement in attitudes and self-reported practices. Analysis of cost data revealed wide variation across the program. Implementation costs (those associated directly with the number of classroom instruction hours) accounted for more than 90% of the total costs and were, in turn, related to program effectiveness. Analysis of effects-to-classroom hours revealed that, while relatively few hours of instruction can produce large effects for knowledge, more hours are required for the development of attitude and practice effects, and that stable effects are established for all three domains at about 40–50 classroom hours.