British school language (6)
I believe the answer is:
breton
'language' is the definition.
(Breton is an example)
'british school' is the wordplay.
'british' becomes 'br'.
'school' becomes 'eton' (famous UK public school).
'br'+'eton'='BRETON'
(Other definitions for breton that I've seen before include "Language of NW France" , "A native of Brittany, France" , "Frenchman" , "Inhabitant of NW France" , "Person from Brittany" .)