The effectiveness of Mississippi's Assistant Teacher Program (ATP) was evaluated after its third year of operation, determining: (1) whether first graders who were exposed to teachers and assistant teachers who had been in ATP for three years continued to make progress in academic achievement; (2) the effectiveness of ATP in fostering achievement among second graders who had been ATP participants for two years; and (3) the overall effect on third grade achievement of three years of ATP experience versus no exposure. The Stanford Achievement Tests (SAT) measured achievement in reading, mathematics, and language arts. Scores were compared with previous test results and with national norms. The SAT was administered to 42,579 first graders, 4,556 second graders, and 4,454 third graders. Results indicated a decline in first grade scores, perhaps due to the change in achievement tests used. First grade scores were above the national norms in reading and language, but below in mathematics. Second graders' achievement was similar to the previous year, and was above the fiftieth percentile in national norms. Achievement of third graders with three years of ATP experience exceeded nonparticipants' achievement. It was concluded that the program was highly successful. Further study of the first grade curriculum and test results was recommended. (GDC)