Determined for son to go to public school (3,2)
I believe the answer is:
set on
'determined' is the definition.
(I've seen this before)
'son to go to public school' is the wordplay.
'son' becomes 's'.
'to go to' means one lot of letters go next to another.
'public school' becomes 'eton' (I've seen this before).
's'+'eton'='SET ON'
'for' is the link.
(Other definitions for set on that I've seen before include "Go" , "Attack" , "Determined" .)