Brings up the back at school (5)
I believe the answer is:
rears
'brings up' is the definition.
('rear' can be a synonym of 'bring up')
'back at school' is the wordplay.
'back' becomes 'rear' (something's rear is its back).
'at' means one lot of letters go next to another.
'school' becomes 'S'.
'rear'+'s'='REARS'
'the' is the link.
(Other definitions for rears that I've seen before include "bucks" , "Sets up" , "Fosters, brings up" , "Raises" , "Back ends" .)