A hyperactive child may blow through a test
(and get them all right or all wrong). The ADHD
child will never finish the test
(at least until, they have learned they will always fail and they just give up or mark things that don't make sense). I have had kids that I gave 3 days to take a test, and they barely finished.
Homework is probably one of the best clues. If most kids take one hour for homework, the ADHD child will take 3 hours and probably still not be done.