When an effective teacher joins a grade-level teaching team, student learning improves across the board as other teachers in the grade raise their game, finds a study of Miami-Dade County, Fla., schools.
Researchers from the University of Washington, Stanford University, and Vanderbilt University examined teacher “spillover” effects using more than a decade of administrative data on math teachers in grades 3-8 and their students’ standardized-test scores in the Miami district.
Novice teachers were excluded from the analysis, so the researchers could compare teachers already in the school with those who were new to it but had previously taught the same grade level, based on their previous students’ test scores.
The researchers found strong evidence of positive spillover effects: If a transfer teacher joined a grade-level team and was one standard deviation more effective than an incumbent teacher, the students in the incumbent teacher’s class also saw an increase in math scores, the data analysis found.
But the opposite did not hold true: When an ineffective teacher joined the team, it did not disadvantage the incumbent teachers’ students.
Therefore, mixing teachers with diverse performance levels in the same grade levels can boost student achievement, the researchers conclude.
