How pupils end up dead cute with exercise (8)
I believe the answer is:
educated
'how pupils end up' is the definition.
(pupils receive an education)
'dead cute with exercise' is the wordplay.
'with exercise' indicates anagramming the letters (letters exercise or move around).
'dead'+'cute'='deadcute'
'deadcute' anagrammed gives 'EDUCATED'.
(Other definitions for educated that I've seen before include "Learned - cultivated" , "Schooled, trained" , "Trained; learned" , "Clever" , "Having completed schooling, well informed" .)