Do Students Learn More with an Additional Teacher in the Classroom? Evidence from a Field Experiment

We present a field experiment investigating treatment effects of an additional teacher in the classroom on student learning. The treatment targets literacy instruction during first and second grades. Nearly 6,000 students in 300 classrooms participated in the experiment. The treatment has on average no effects on student learning. However, boys seem to benefit, with treatment impacts of about 0.12 and 0.09 standard deviations on the national literacy assessment and the reading self-concept, respectively. The effects seem to be particularly large for boys with low skills at baseline, with treatment impacts of 0.23 and 0.22 standard deviations.