From Longman Dictionary of Contemporary Englishschool friendˈschool friend noun [countable] especially British English SSCa friend who goes to the same school as you
Examples from the Corpus
school friend• Various willing hands, including her school friend Balie Waggener joined in the project.• There she was able to board with the family of an old school friend.• He phoned an old school friend named Andy Rourke.• She was an old school friend, although we were out of school by then.• I share digs with an old school friend of mine, Daphne Harcourt-Browne. 