Polluted school - is one enrolled? (8)
I believe the answer is:
poisoned
'polluted school' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Perhaps you can see a link between them that I can't see?
'is one enrolled?' is the wordplay.
I cannot really understand how this works, but
'is' is within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for poisoned that I've seen before include "Administered a toxin" , "Administered venom" .)