Moral sense against discipline at school (10)
I believe the answer is:
conscience
'moral sense' is the definition.
('conscience' can be a synonym of 'moral sense')
'against discipline at school' is the wordplay.
'against' becomes 'con' (I've seen this before).
'discipline at school' becomes 'science'.
'con'+'science'='CONSCIENCE'
(Other definitions for conscience that I've seen before include "moral insight" , "having moral standards" , "Sense of morality" , "Inner voice" , "morals" .)