preppy
Concise Oxford English Dictionary © 2008 Oxford University Press:
preppy /ˈprepi/ (also preppie) N. Amer. informal
▶noun (pl. preppies) a pupil of an expensive preparatory school. ▶adjective (preppier, preppiest) of or typical of such a person, especially with reference to their neat style of dress.
'preppy' also found in these Oxford entries:

