We can all agree that teachers contribute in many ways to students' lives. But how should we measure those contributions? Answers are all over the map, from test-based evidence of teachers' contribution to student learning to observers' perceptions of how well they build rapport with their students. Is there some middle ground where we can measure something beyond test scores?

An updated working paper by Jing Liu and Susanna Loeb (of Brown University) finds a plausible way to quantify at least one key contribution made by teachers: getting students to show up to class. They refer to this as "attendance VAM," a measure of teachers' individual effect on student attendance, with similar controls built into the model as the more familiar, learning-based VAM.

They first examined this issue in a 2017 paper, finding that teachers do vary significantly in their effect on student attendance. For example, when a student's teacher is one standard deviation above average in "attendance VAM," that student has about half as many unexcused absences as she would if her teacher had an average attendance VAM.

Since then, the researchers revisited the data and unearthed some useful nuance. This time, they find that different teachers have a bigger impact with different sets of students. The groups of students who benefit most from having a teacher with a high attendance VAM are those who are behind on the path to graduation and who have lower rates of attendance. But, these differences, while statistically significant, aren't very large, hardly meriting schools reassigning teachers to certain classes based on their "attendance VAM."

The more compelling addition is that the attendance VAM findings are driven by the teachers with the lowest attendance VAM. In other words, most teachers are decent at encouraging their students to come to class, but some teachers seem to be really bad at it. This suggests that teachers' attendance VAM may be a feasible, and entirely relevant, measure to evaluate a teacher's performance (at the secondary level), one that matters for student outcomes and has nothing to do with test scores.

Of course, an evaluation system would have to take into account how students' attendance looked not only in previous years but in the same students' other classes in order to isolate that teacher's impact on that student. Otherwise teachers would be penalized for teaching students who have chronically skipped class.

But, if this measure can help identify and reward those teachers who are effectively encouraging kids to show up to class every day, especially those kids who have been falling behind, then it seems like one worth considering.