I show HN and YC to my middle school students and tell them a little about it. I just want them to see it. They'd rather spend time reading snopes if that makes you feel any better. ;) The only time I've heard of a middle school kid going back on his own was when one kid showed it to his dad, who was thinking about starting his own business.

I spend more time going over HN and YC with my high school students. I don't have time to teach them how to do their own start-up in class. But I want them to be exposed to the idea, and know some places to go for more info if they take to the idea, want to learn why I've ruined their life by teaching them Java, or whatever. :)