What is a good, simple song to teach a beginner guitar student?
As far as teaching kids this young your best bet is to stick with simple 2 or 3 chord folk songs and campfire songs. Buy a book of these type of songs and teach him as many as he can learn. The idea is to get them playing as many basic chords as possible. Quantity over quality. Just because you think a song is cool does not make it so in the mind of a second grader. This is a child so try songs that were written for children, that he might have heard in school. He might want to take his guitar to show-and-tell and play some songs that the other kids know already. Try to find out from his parents or teacher what songs his class sings. I barely remember 2nd grade but I know that singing and listening to kid songs was a part of the fun.