i think this is a little ridiculous singling the kids out like this. at my college it was a requirement that EVERYONE take 6 gym credits. there were tons of different ways to do it, i took self defense, ballroom dancing, and squash, but there was also that fitness for life program that they talk about in that article. except at my school everyone had the option of taking it and some people (even the normal weight people) loved it because it was nutrition based. i hated the fact that i had to take gym, but now i kind of miss it. i wish i had that access again to take a class a learn a new sport. my friends and i used to play squash together on the weekends, which was totally self motivated, after we learned how to play in class. i think singling kids out will not motivate them to lose weight at all. if they learn along with their peers, it might be a different story, but then again, they might get discouraged because they can't do what their normal weight peers can do.
it might be better if they have an optional class that overweight people can sign up for that would make them feel more comfortable in group of people who are at the same activity level that they are. if they don't want to take that class, they can sign up for a class with the normal weight students. (kind of like a regular gym, versus going to curves, some women feel more comfortable without men at their gym, and that's OK!)