reform schoolnoun [ C ]
uk/rɪˈfɔːm ˌskuːl//rɪˈfɔːrm ˌskuːl/US also reformatory, /rɪˈfɔːm.ə.tər.i//rɪˈfɔːrm.ə.tɔːr.i/(especially in the past) a type of school where young people who have broken the law are sent instead of prison:
His first conviction, for burglary, sent him to reform school at age 10.