Stanford psychologist Carol Dweck has a great overview of her work on what motivates people -- and kids, in particular. Here's an excerpt:
In addition to encouraging a growth mind-set through praise for effort, parents and teachers can help children by providing explicit instruction regarding the mind as a learning machine. Blackwell, Trzesniewski and I recently designed an eight-session workshop for 91 students whose math grades were declining in their first year of junior high. Forty-eight of the students received instruction in study skills only, whereas the others attended a combination of study skills sessions and classes in which they learned about the growth mind-set and how to apply it to schoolwork.
In the growth mind-set classes, students read and discussed an article entitled “You Can Grow Your Brain.” They were taught that the brain is like a muscle that gets stronger with use and that learning prompts neurons in the brain to grow new connections. From such instruction, many students began to see themselves as agents of their own brain development. Students who had been disruptive or bored sat still and took note. One particularly unruly boy looked up during the discussion and said, “You mean I don’t have to be dumb?”
As the semester progressed, the math grades of the kids who learned only study skills continued to decline, whereas those of the students given the growth-mind-set training stopped falling and began to bounce back to their former levels. ...
Here's a previous post on Dweck's research.