Not at all sure but I'd love to hear the answer. I don't see anything obvious on their website, but I assumed you had already checked there. My son just signed up for the AMC10 on the advice of his pre-calc teacher. My DS doesn't usually need extra time for math tests and it isn't written into his 504. I am only encouraging him to try it for the fun of it & because I am a bit curious how he will do.
We are still considering if we should request extra time on the SAT's for my son. I do know one can request extra time on the SAT & ACT tests, the downside that I'd heard is that it is notated on their scores that extra time was taking.
