Some youth leagues have that rule now about bringing home good report cards.
Someone stole my idea.

But none of the really adhere to the rule come game time.
...and that's where my implementation of my idea would be different. You fail a test and it's the day before the "championship" game? Guess what dude, you're sitting the bench. Why? Because it's your responsibility to the team to do the best you can on a test. A parent doesn't like that? Give them the AAU's phone # and hold the exit door open for them.

Little Johnny Superstar would either sit the bench and have a book cracked open studying, or he'd be on his way out the door. If a parent questioned that decision, then they definately wouldn't have their priorities straight and I'd personally tell them as much.