A statewide sustained effort to improve student learning in Missouri by adopting and adapting promising research-based educational practices is described. The concept of an Instructional Management System (IMS) with desired learner outcomes determining both instruction and testing was suggested to local school districts beginning in 1980. In 1985, legislation provided both funds and authority to engage large groups of teachers to create criterion-referenced tests in reading/language arts, mathematics, science, and social studies/civics for various age groups. The refinement process that resulted in the Missouri Mastery and Achievement Test batteries is described. The achievement gains of large populations of students as measured during the first 2 years for which comparative data were available are also reported. The process of periodic review and revision is also briefly described. Four tables and one figure provide achievement data. (Author/SLD)