Don't know about acc...but for maths, it is pretty hard for them to tell who actually did your test (which is why they aren't worth that much). The reason for the tests is to make sure you learn how to do stuff that will be on the in-class tests. Most people seem to have a go at a test, then go and ask friends/tutors about anything they got wrong before having another go. Do you still get as many goes as you like?