Quietly representative sort of school? (4)
I believe the answer is:
prep
'sort of school?' is the definition.
'quietly representative' is the wordplay.
'quietly' becomes 'p' (musical symbol).
'representative' becomes 'rep' (rep is a kind of representative).
'p'+'rep'='PREP'
(Other definitions for prep that I've seen before include "Homework (abbrev.)" , "warm-up race" , "Homework (abbr.)" , "School work done outside lessons" .)