The Missouri Mastery and Achievement Tests (MMAT) were developed as a result of the Excellence in Education Act of 1985, which required the state department of education to identify core competencies and key skills in reading/language arts, mathematics, science, and social studies/civics and to test a sample of students annually. State-level data on these tests is currently reported for grades 3, 6, 8, and 10. Approximately 50,000 students for each grade take these tests in grades 3 and 6, and about 5,000 students for each grade (approximately 10% of Missouri students) take the MMAT for grades 8 and 10. Spring MMAT results indicate that student achievement has leveled off in recent years, with students showing little or no improvement across most grade levels or subject areas since the implementation of the revised tests in 1991 and 1992. In relation to the initial testing in 1987, scores are up, suggesting that the tests have had positive impact on achievement. The 1996 MMAt results are somewhat encouraging in that they reflect improvement over 1987, but they reflect little recent change. (Contains 20 tables.) (SLD)