Interesting analogy. I would say the danger isn't quite in students injuring themselves in the classroom as much as it is giving destructive chemicals to students. Sure some of them can handle it, but the deviant ones will create havoc given the opportunity. In football there is a certain physical discipline allowed, where as in science its just the principals office, which can be better than class. Good analogy, but I think far from raising the argument...
Although this is the more hands off approach, if you have a mac, get familiar with RapidWeaver. I actually started learning web design with RapidWeaver and it was great. Since then I moved onto writing my own code and I discovered that using custom code inline with RapidWeaver is a great approach. Rather than rip off other ideas, gain powerful functionality and create your beautiful design.
I like the concept just because it is built around twitter. I don't tweet myself, but I feel like it adds something to the twitter experience. There was an article talking about how twitter only has a 25% retention rate in their second month and sites like this might help that number get better.
High school is rough, especially for those intelligent enough to be reading hackernews. Its pretty far from a reality of the world and I would say appreciate the lack of responsibility expected of you and learn a programming language as well as a musical instrument. And even start learning a foreign language as well as SAT vocab cards during class. Also, I recommend skipping a lot. It got me through :)
What a cool application. I would love to be able to use it without paying when you do launch. I find that learning Chinese on there becomes enticing, and there is a certain feeling that I am playing a game. I don't think it would hurt to have a ten character demo on the front page with a full tutorial for the Chinese and computer illiterate. That may hook inidividual users, especially if you can buy in at a good rate for starter packages. It seems like you guys are trying to exclusively appeal to the very intent on learning Chinese people, but even from your testimonials it seems that Skritter is a good pass time, even for those not studying Chinese and just want an easy, fun way of drawing chinese letters. I think offering a startup package for cheap will draw a lot of people, and as I have found out, you will soon get hooked.
Also, it may be sweet to add little quiz games to Skritter. Like timed strokes, or something fun (you appear to be creative) to really entice people and motivate them to move on to the next lesson. It always feels better to conquer something like that in an online learning app... And finally, please tell you guys are planning an iPhone app?