DH and I pay our kids for good grades...well, actually, only for the grades over 90, anything between 80 and 90 there is no money exchange, and for anything under a 70, they pay us!
It might sound odd, but it works for us. When my older son was looking at high schools, he picked an expensive catholic high school, one which we could not afford, my DH decided then that if he saves us money on the tuition, we will pay him for it. So if he got a scholarship, he would get a laptop (he did, and he got the laptop) Then to keep the scholarship each year, his average gad to be over a 90, so we started the pay for grades thing... if he lost the scholarship, the school would cost us alot, so we were very interested in him doing well.
Four years later, he is graduating this June, and has already been awarded 1000's of dollars in college scholarshios, he just needs to choose where to go, and the tuition is paid for him.
Now that my younger son is getting ready for high school, he wants the same school, so he approached us asking for the same deal as his older brother.