year’s worth of classroom experience with an ineffective teacher. Conversely, a child who spent one year with a highly effective teacher tended to experience academic benefits even two years later. In this and other studies, Sanders and his colleagues have shown that placing students in classrooms with high-quality teaching does matter. Variables such as the racial and/or ethnic composition of schools, students’ socioeconomic levels, and the mean achievement of an entire school correlated far less with student achievement when compared to the variable of teacher quality.

In a large-scale study of younger children in grades 3-5, Sanders and colleagues Wright and Horn found that “teacher effects are dominant factors affecting student academic gain,” especially in mathematics but also, noticeably, in science (Wright et al., 1997).

In a 1991 study, Ferguson examined student scores on standardized tests in reading and mathematics, teacher qualifications, and class size in 900 out of 1,000 school districts in Texas. The teacher qualifications examined in each district included teacher performance on the Texas state teacher examinations, years of teaching experience, and teachers’ acquisition of advanced (master’s) degrees. Ferguson (1991) found that the following teacher qualifications, listed in order from most to least important, had statistically significant effects on student scores: teacher language scores on the state examination, class size, years of teaching experience, and the earning of an advanced degree. According to a review of the study conducted by the National Center for Education Statistics (cited in Sparks and Hirsh, 2000), teacher expertise, as Ferguson had defined it, explained 40 percent of the variance in the students’ achievement in reading and mathematics.

Later, in 1996, Ferguson and Ladd used Sanders’ statistical approach to study nearly 30,000 Alabama fourth graders during the 1990-91 school year. They found that students’ test scores in mathematics and reading were positively affected by two teacher variables: higher than average scores on the American College Testing program’s college entrance examination and completion of one or more master’s degrees.