The good, the bad and the average

"We study the scale and nature of ability peer effects in secondary schools in England. In order to shed light on the nature of these effects, we investigate which segments of the peer ability distribution drive the impact of peer quality on students' achievements. Additionally, we study which quantiles of the pupil ability distribution are affected by different measures of peer quality. To do so, we use census data for four cohorts of pupils taking their age-14 national tests in 2003/2004-2006/2007, and measure students' ability by their prior achievements at age-11. We base our identification strategy on within-pupil regressions that exploit variation in achievements across the three compulsory subjects (English, Mathematics and Science) tested both at age-14 and age-11. We find significant and sizeable negative peer effects arising from students at the very bottom of the ability distribution, but little evidence that the average peer quality and the very top peers significantly affect pupils' academic achievements. However, these results mask some significant heterogeneity along the gender dimension, with girls significantly benefiting from the presence of very academically brig