Seventeen year old boys looking to get a laugh in class will use whatever tool is at hand. Well, normal seventeen year old boys anyway. It's just means he's a pedestrian comedian who goes for the low-hanging fruit.

The part about you lecturing him makes me laugh. My oldest (28) son was reminding me just last week about the time I read the lyrics on his Woo-Tang Clan CD and "spoke" with him about why "nigger" is not ok to say regardless of what color you are. "All I kept think was when is he going to shutup!"

But, if you can talk your son out of being seventeen my hat's off to you.