Principals have a potentially huge lever to reduce educational inequity: classroom assignment. At a minimum, kids who are already behind shouldn't systematically be assigned to less effective teachers than their peers. But how do principals actually use this lever? A recent study by Demetra Kalogrides, Susanna Loeb and Tara Beteille attempts to find out, and in the process raises important questions for researchers and policy makers.

Most research on classroom assignment patterns looks at district-wide data. Kalogrides and her co-authors focus on assignment patterns at the school-level, showing how specific characteristics of a school's principal and faculty appear to drive who gets to teach which students. Here are a few of its conclusions, which are based on analysis of Miami-Dade schools:

• As previous studies have found, Kalogrides et al. show that less experienced teachers tend to get assigned kids who are farther behind. But their study shows that this pattern is even more pronounced in schools with a high share of experienced teachers. A first-year teacher teaching in a school with a below average percentage of veteran teachers is generally assigned kids who are about a month behind the kids of 15-year veterans. But the kids assigned to first-year teachers in schools with an above average percentage of veterans are about two months behind.
• Principals of schools with high percentages of struggling students aren't so quick to give kids on or above grade level to veterans. These principals assign first-year teachers kids who are about two weeks behind the kids of 15-year veterans. In schools with average levels of proficiency, the students assigned to first-year teachers are about six weeks behind those of the 15-year veterans.
• Minority teachers tend to be assigned students who are further behind the students white teachers in the same school are assigned. This tendency is particularly pronounced in schools with an above average quotient of white teachers.
• Teachers who have attended more selective colleges as measured by their average SAT/ACT scores tend to get higher achieving students than those who did not.

As the authors of the paper point out, it's hard to know just what to make of these classroom assignment patterns. One could argue that principals know that experience and the selectivity of where one went to college are useful proxies for effectiveness, and that they are rewarding these teachers with higher achieving students, who are presumably easier to teach, in an effort to retain them. Principals might be assigning minority teachers to minority students, who also tend to have lower proficiency rates, because they may believe that they could be more effective with students with similar backgrounds.

On the other hand, it could be that these classroom assignment preferences reflect prevailing patterns of privilege. Principals assign higher-achieving students to experienced teachers, to white teachers and to teachers from selective schools not as part of an HR strategy but simply because they believe that these teachers are "entitled" to them. That these patterns are more pronounced in schools where there are greater proportions of higher status teachers (e.g., more experienced, more white) gives some credence to this interpretation.

Clearly, districts need to look at the data to find out just which teachers are effective and how they and their students are being sorted. As more evaluation systems come on line, this will be easier to do. If classroom assignment patterns show that lower-achieving students are being systematically shortchanged, then districts should take action. In the meantime, a qualitative study of how and why principals make the classroom assignments they do would be a valuable counterpart to this study.