This is an interesting topic!
Our view is that each member of the family has jobs to do to keep the family running. This includes income generating work as well as non-remunerated, but equally important, tasks for the household. DDs primary job is doing well in school and she also has chores to do around the house.
In exchange for being a member of the house, each member gets a monthly allowance for personal purchases. This allows each of us to get the things we want without a lot of discussion or negotiation.
DD12 receives an allowance which is $1 per week per year of age. This is for gifts, personal purchases, snacks / Starbucks when shes out with friends, music, makeup etc. Wants basically. We don't specifically pay her for grades or chores though because with our little future lawyer we'd never hear the end of the negotiating. Instead, if she does a bad job (which at this point is more likely to be "forgetting" chores rather than bad grades) she can be penalized by losing allowance.
This year we got her a checking account and a check card for that money. If she overdrafts (which she has not because she's very careful) she has to cover it. We also started giving her a specific clothing allowance in savings. I still buy coats and boots, but she buys the rest (she's a much better shopper when it's her money). This has greatly reduced the stress of shopping with her because if she wants to spend her whole amount on one cool item, that's her prerogative. Gift money (from grandparents typically) and earnings (babysitting) go into her savings. It tends to build without her noticing until a trip or something else large she wants.
We do still buy things for her from time to time without insisting on payback. Books, for example, but it's a surprise and gift rather than an obligation.
