Pupils showing sophistication (5)
I believe the answer is:
class
I believe this clue is a double definition.
'pupils' is the first definition.
(I've seen this before)
'sophistication' is the second definition.
(I've seen this in another clue)
'showing' is the link.
(Other definitions for class that I've seen before include "Group - style" , "People having the same social or economic status" , "pupils?" , "Category (of things)" , "sort" .)