The purpose of this study was to determine whether high school seniors (N=492) had attained each of five selected earth science concepts and if said attainment was influenced by the number of science courses completed. A 72-item, multiple-choice format test (12 items for each concept) was developed and piloted previous to this study to measure these concepts: (1) cause of the seasons; (2) interdependence of man and environment; (3) changing earth; (4) day and night; and (5) solar energy. Concept attainment was arbitrarily set at 80%, which translates to 9.6 questions being answered correctly for each set of 12 items per concept. Significant differences in concept formation were observed across the sample and found to be influenced by the quantity of science courses the seniors had completed. While expected, these results lend credence to the notion that secondary science curricula stress concepts and their application. (Author/JN)