This report examines the top Third International Mathematics and Science Study-Repeat (TIMSS-R) performers and compares Delaware classroom environments with those of the top performing students. Data analyses show that Delaware's average class size is larger than any of the top performers, and student attendance, skipping, and tardiness problems are more severe in Delaware than in any top performer. The majority of Delaware students are taught mathematics by teachers who did not major in mathematics or mathematics education, which is different from the top performers. It is shown that teachers' professional development opportunities are not as plentiful in Delaware as in the top performing schools, and teachers in the top performers participate in significantly more professional classroom observations than Delaware teachers. (KHR)