Wake selected pupils after mistake (10)
I believe the answer is:
slipstream
'wake' is the definition.
(the current created behind a vehicle)
'selected pupils after mistake' is the wordplay.
'selected pupils' becomes 'stream' (I've seen this before).
'after' says to put letters next to each other.
'mistake' becomes 'slip' (synonyms).
'stream' put after 'slip' is 'SLIPSTREAM'.
(Other definitions for slipstream that I've seen before include "Air behind a moving vehicle" , "Draught" , "Closely follow" , "Air behind any quickly moving object" , "Air current" .)