A school district leader with money for teacher bonuses faces a choice: Should she spread the money around to all teachers equally or give more to teachers who have performed best?

A new study, released by the federal government, suggests that merit-based bonuses are the way to go, as they help raise student test scores without making a significant dent in teacher morale.

The result? The schools that gave performance bonuses boosted student test scores throughout the four years of the study, between 2011 and 2015.

The research focuses on a federal program known as the Teacher Incentive Fund, and compares schools that gave all teachers an automatic 1 percent bonus to those schools that gave bonuses based on classroom observations and student test scores. About 130 schools across 10 districts were randomly assigned to one of the groups.

The differences between the two groups of schools weren’t big, and they were only sometimes statistically significant. For instance, in year three of the study, performance pay increased student test score performance by 2 percentile points.

But because the program was relatively cheap to implement, performance bonuses were very cost effective.

Read the full article on performance bonuses by Matt Barnum at Chalkbeat