Teaching both girls and boys (2-2)
I believe the answer is:
co-ed
'teaching both girls and boys' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for co-ed that I've seen before include "Teaching attended by both sexes" , "School for both sexes" , "Teaching both girls and boys" , "School for boys and girls, in short" .)