Districts are increasingly making personnel decisions based on teachers' impact on student-achievement gains and classroom observations. In some schools, however, a teacher's practices and their students' achievement may reflect not just individual but collaborative efforts. In other settings, teachers' instruction benefits less from the insights…

This year the Center on Education Policy (CEP) analyzed data on the achievement of different groups of students in two distinct ways. First, it looked at grade 4 test results to determine whether the performance of various groups improved at three achievement levels--basic and above, proficient and above, and advanced. Second, it looked at gaps…