WordNet sense 1 (a league ranked by quality):

division

WordNet sense 2 (a body of students who graduate together):

year

WordNet sense 3 (a body of students who are taught together):

form, grade

WordNet sense 4 (a collection of things sharing a common attribute):

category, family

WordNet sense 5 (people having the same social or economic status):

social class, socio-economic class

WordNet sense 6 (education imparted in a series of lessons or meetings):

course, course of study, course of instruction

WordNet sense 7 (arrange or order by classes or categories):

assort, classify, separate, sort, separate, sort out