Scorn during school tests — they inflict unnecessary pain (7)
I believe the answer is:
sadists
'they inflict unnecessary pain' is the definition.
The definition suggests an adverb but the answer is not.
'scorn during school tests' is the wordplay.
'scorn' becomes 'dis' (I can't explain this - if you can you should believe this answer much more).
'during' indicates putting letters inside.
'school tests' becomes 'SATs' (scholastic assessment tests in the UK).
'dis' inserted into 'sats' is 'SADISTS'.
Can you help me to learn more?
(Other definitions for sadists that I've seen before include "people with a mean streak" , "Perverted pain-inflicters" , "Brutes" , "They like to hurt" , "They take pleasure form inflicting pain" .)