"Cohort size" refers to the number of people in a particular group or class. It indicates how many individuals are in a specific category or enrolled in a program or course together. Full definition
The estimate assumes a minimum cohort size of 10 and that sufficient schools are in the programme to make it viable. (educationendowmentfoundation.org.uk)
The mean cohort size was 212, and the mean pass rate on the 8th - grade math exam was 56 percent. (educationnext.org)
The most striking difference across school types involves cohort sizes (the average number of students in each grade). (educationnext.org)