This research study investigated the effect of the participation of science and mathematics teachers in the National Science Foundation (NSF) Institutes upon the achievement of junior and senior high school students. A randomly selected group of junior and senior high school science teachers and randomly selected classes of theirs were administered achievement tests in science. Chi square and analysis of covariance (ANCOVA) were used to analyze the data. Participation in NSF Science Institutes and geographic regions were factors in a two-way ANCOVA. Class mean for achievement was the dependent variable and teacher achievement was the covariate. NSF participation was found to be a significant factor in student achievement for high school teachers but not for junior high school teachers. The study was replicated for mathematics teachers and classes and the same results were found. It was concluded that significance at the senior high school and nonsignificance at the junior high level may be due to the difference in subject matter taught and the population of students between the two levels. (Author/HM)