Positive Assortative Teaching

There’s an old quip: ask three teachers how to fix schools and you’ll get at least 4 different opinions. It’s not common to find consensus in education, but one idea almost everyone can agree on is that great teachers are key. Research finds that teacher quality is the single largest in-school factor determining a child’s academic success. So policymakers are obviously interested in keeping the best teachers in the classroom and using them effectively.

The consensus breaks down when the conversation turns to how to keep great teachers in the classroom. One difficulty is that education reformers generally don’t know much about the attitudes and opinions of top performers. The largest teacher surveys don’t distinguish between responses from top, average, and bottom performers (privacy concerns make it difficult to link large student data sets to qualitative information about teachers). Instead, researchers rely on staffing datasets to intuit the factors that cause teachers to leave the profession.

In “Teacher Quality and Teacher Mobility,” authors Li Feng and Tim Sass use staffing data to examine factors that made Florida teachers more likely to change schools or exit teaching between 2000 and 2004. Their findings offer equal parts hope and heartache for school leaders.

Across the state, the highest and lowest performing teachers were most likely to leave their schools by transferring to another school or leaving the profession all together. Average teachers, those in the 2nd and 3rd quartile, were about 20 to 30 percentage points more likely to stay in teaching than their peers on either end of the spectrum. So although teacher retention isn’t a race to the bottom, it’s certainly no race to the top.

The picture dims, though, when Feng and Sass look at how teachers compared to their colleagues within the same school. They find that the highest performing teachers were more likely to leave than were their lower performing peers. This means that across the state, the best and worst teachers are leaving at similar rates, but within an individual school the best performers are more likely to leave than their lower performing colleagues.

One explanation for this phenomenon could be that teachers prefer to work with colleagues who have similar skills. Feng and Sass seem to offer some support for this view. Among those who left their schools, the lowest performing teachers disproportionately transferred into schools with a high proportion of low performers and high performers disproportionately transferred into schools with a high proportion of high performers.

Feng and Sass’s work does not point to any obvious policy solutions, but one observation seems clear: environments matter. Notably, Florida schools with a higher proportion of professionally certified teachers and more experienced staff did a better job keeping their best teachers in their classrooms.