Findings of studies which looked at the effectiveness of the individualized instruction teaching approach are synthesized. After a search of several computer databases and of bibliographies of reports, the researchers located a total of 51 usable studies. Each of these was published after 1955, was relevant to grades 6 through 12, had both control and treatment groups, and suffered from no major methodological flaws. Study outcomes were examined in four different areas: student achievement as measured on final course examinations; student achievement on examinations in critical thinking; favorability of student attitudes toward subject matter of a course; and student self-concept. Instead of a simple descriptive review, a meta-analytic technique was used to synthesize the findings. In this meta-analysis the outcomes of the studies were described in a quantified form, the studies were coded according to their significant features, and the quantified outcomes were related to the significant features of the studies. Results showed that individualized systems of secondary school teaching have not met the great hopes they once raised. Of the 49 studies reporting final exam scores, only 12 showed statistically significant differences due to teaching method and 4 of these were in favor of conventional teaching. Results for critical thinking, self-concept, and student attitudes were similarly negative. (RM)