This is a good question and things like this need to be asked in view of the current state of affairs in our education system. In light of this, let me make a few comments.
First, it is a good to use incentives to educate young people. To be sure, education and learning itself should be its own reward, but in the real world some incentives might be a good idea. In light of this, happy meals from McDonald's might work. In the least we can say that there is a step in the right direction in that people are thinking about how to make the educational system stronger.
Second, happy meals might not be the best choice. As you probably know, fast foods are not the most healthy. I would think that the school would want to make more responsible choices when it comes to foods as rewards. Moreover, this would add to our obesity problem. Therefore, with some thought, there can be better incentives and choices. How about an honors course? How about an academic sleepover camp. The sky is the limit in terms of creativity. In light of this, I would think that better incentives could be offered.