preppie
noun[C]
(alsopreppy)us/ˈprep·i/apersonwho is or was astudentat apreparatoryschool(=privateschoolthatpreparesstudentsforcollege), or someone whodressesin thetraditionalstyleof suchstudents:
Dressed like a preppie, shewearsapleatedskirt,cottonshirt, andkneesocks.