Expel student and put him in prison (4,4)
I believe the answer is:
send down
This clue is a double definition.
'expel student' is the first definition.
'put him in prison' is the second definition.
'and' is the link.
(Other definitions for send down that I've seen before include "Sentence to a prison term" , "Dismiss student" , "Assign time to" , "bang up" , "Expel (from university)" .)