Ah yes, the good ol' parental schoolwork bribe. First, please make sure you are totally prepared for the responsibility of caring for a hedgehog - a proper size cage, wheel, food, heat source, bedding, etc. It's not a decision that should be made just a week in advance if you don't know what to expect.
But if you're all set in that regard, it depends on what areas you have room for improvement, academically. What grade are you in? You could give your dad a heads up about an upcoming test and make a deal with him to get a certain grade. Of course, that may mean putting off getting a hedgie for a little bit.
Hedgie Mommy to little Piglet
* Abby *