(n.) A pupil who attends the same school as another.

ace amigo associate bedfellow bedmate birthmate bosom buddy buddy bunkie bunkmate butty camarade chamberfellow chum classmate clubmate colleague comate companion company compeer comrade confrere consociate consort copartner copemate copesmate couchmate cradlemate crony cupmate fellow fellow student general partner girl friend gossip grade schooler high schooler infant intermediate schooler jailmate kindergartner mate messmate nursery school child old crony pal pard pardner partner pewmate playfellow playmate prep schooler preschool child preschooler primary schooler roommate school child school kid school lad schoolboy schoolfellow schoolgirl secondary schooler secret partner shelfmate shipmate shopmate side partner sidekick sidekicker silent partner sleeping partner special partner tablemate teammate tentmate watchmate waymate workfellow yokefellow yokemate