Seth Gershenson and Laura Landbein (American University)
“The Effect of Primary School Size on Academic Achievement”
http://journals.sagepub.com/doi/full/10.3102/0162373715576075
“Two subgroups of interest are significantly harmed by school size: socioeconomically disadvantaged students and students with learning disabilities. The largest effects are observed among students with learning disabilities: A 10-student increase in grade size is found to decrease their math and reading achievement by about 0.015 test-score standard deviations.”
“The most striking result in Table 6 is that students in larger schools who have administratively classified learning disabilities perform significantly worse on math and reading standardized tests. The interaction effects are similar in magnitude for both math and reading, indicating that a 10-student increase in total grade enrollment reduces the achievement of learning-disabled students by about 0.015 test-score SD. This is an arguably practically significant difference, as the sample SD of grade enrollments is about 40 students and the average annual change in grade enrollments was 11 students.”