The purpose of this study was to examine the relationship between high school achievement and selected student, family, peer-group, teacher, and school characteristics. The school was used as the unit of analysis;The sample consisted of 565 public high schools from the High School and Beyond (HS&B) national longitudinal study. HS&B is a study of high school sophomores and seniors in the United States;Variables from each area were found to be significantly related to high school achievement. Specifically, student, family, peer-group, teacher, and school variables explained, respectively, 52, 47, 16, 9, and 31 percent of the variation in achievement. A total of 66 percent of the variance was explained when all the variables were combined. An examination of the unique effect of each area on achievement indicated that student characteristics explained more unique variance than any other area. The second greatest unique contributor was the area of family characteristics;A supplementary focus of the study was to use available data and test a proposed high school achievement model. The results indicated that high school achievement could be explained directly by school, peer-group, and student characteristics, and also indirectly by family, teacher, peer-group, and student characteristics. The ecological fallacy of aggregate data was discussed and further research was recommended.