Taught again to accept school's head being aloof (10)
I believe the answer is:
restrained
'aloof' is the definition.
(thesaurus)
'taught again to accept school's head' is the wordplay.
'taught again' becomes 'retrained' ('trained' is an answer for 'taught' so perhaps 'retrained' is OK for 'taught again').
'to accept' is an insertion indicator.
'head' suggests taking the first letters.
The first letter of 'schools' is 's'.
'retrained' enclosing 's' is 'RESTRAINED'.
'being' acts as a link.
(Other definitions for restrained that I've seen before include "Held back" , "subdued" , "Checked" , "Reserved, dispassionate" , "muted" .)