@kirkmanbrandon

This may be quite easy to deal with.

1) find some other teachers in your school who experience this.
2) make sure each of you has a quarter.
3) every time a kid does this in class, do the same, though it will mean something very different.
To wit: the percentage of marks he/she loses off the current assignment every time he/ she tosses the coin.
4) Alternatively, co-opt the practice entirely, rendering it utterly uncool and therefore extinct.

Hope something here helps.