Charter schools are less likely to enroll students with disabilities, and in general they receive less funding for those students, according to a report released Wednesday.

In a review of 18 large and mid-sized school districts across the country, researchers found that at charter schools, students with disabilities represented 9.5% of the total enrollment. At traditional public schools, students with disabilities made up 13.1% of the total enrollment. Traditional public schools also tended to enroll more students with more higher needs, such as students with developmental delays or intellectual disabilities.

Due to the complex formulas states use to calculate special education funding, charter schools on average received 33% less funding for disabled students than traditional public schools, researchers found.