The main purpose of this study was to determine what characteristics of secondary schools were most closely related to the performance of their students on academic aptitude and achievement tests. A 25-item questionnaire on high school facilities, staff support, education and occupation of parents, and characteristics of the community such as size, rate of growth, and presence or absence of community library was distributed to a sample of 844 high schools of varying sizes. 34 variables reflecting school, parent and community characteristics were constructed from the 25 items and four were selected to use in choosing schools to use in the testing phase of the study. These four factors were: 1) teacher experience index; 2) level of training of the principal; 3) percent of last year's graduates to go to college; and 4) percent of support from state aid. 100 schools were selected for testing of academic aptitude and achievement at the ninth grade level and 106 at the twelfth grade level. The Academic Aptitude Test (AAT) tested vocabulary, sentence completion, arithmetic reasoning, and computation. The same 60-item test was used at both grade levels. The achievement tests were in English, social studies, and science, and a different level test was given to the two grades. Tables are presented giving the percentile scores based on both student means and school means. Six school-parent-community variables were isolated which seemed to relate most highly to AAT scores, and various multiple correlation solutions were done to determine the effectiveness of combinations of these six variables in predicting school mean scores on the AAT. The six variables were 1) neighborhood library; 2) percent of support from state aid; 3) instructional support per pupil; 4) percent of fathers who are high school graduates; 5) size of community (rural/urban); and 6) region (South/non-South). The study concludes that "by far the most important item for forecasting level of student achievement within a school is the level of the academic aptitude in the school but that a few of the school-parent-community characteristics may nevertheless add even to this high relationship."