In connection with their investigation of the problems of U.S. secondary education, Dr. James B. Conant and the staff of "A Study of the American High School" wanted to obtain objective evidence on the question whether there are comprehensive high schools which do as good a job of teaching as is done by highly reputed college-oriented schools. Final achievement in trigonometry and physics courses in 13 comprehensive schools and four college-oriented schools was measured by appropriate Cooperative and College Board tests. Ability was held constant in the analysis by scores on SCAT. A very large overlap in the range of teaching effectiveness, as reflected by these tests, was found for the two types of school. The same kind of overlap persisted when the data were analyzed separately for students at three different levels of ability.