What I do with my son is tell him whether it is for being good at school with no problems, having accidents, or even when he eats at home we started a zoo fund. Everytime he does something that is good like no fights for the whole day or no accidents for the day I give him anywhere from a quarter to a dollar to put in his fund.
But now he got carried away and has a Zoo fund, Disneyland fund and a toy fund but it has really improved him. I remind him every morning that if it is a good day he will get money
Just my input