In response to your concerns about erections while in dance class -- don't worry about it! And don't worry about it in performances! You'll find that if you concentrate on your dancing rather than your **** (sorry) the erection problems will fade away. This is from more than 20-years experience in ballet.
First of all remember, we're all human. The human male gets erections. That's nothing to be ashamed about. The fact is that it happens. Secondly, why worry about what people will think about your erections -- it's really none of their business.
The male dancer is their to show his form and technique -- male dancers are not just "porteurs" (to carry/support a ballerina!)!
Trust me, everyone knows what's inside your dancebelt, and the fact that some people care (if they care in the "right" way) should flatter you!
Does it happen to the "pros" in performances? You bet your life it does! Do they worry about it? In my experience, having practiced dance medicine for several years, they don't. They believe in thier art; they believe in their bodies. If the performance is good and the body is in tune, why worry about anything else?
I've been asked to give the "dancebelt lecture" to the new (and some experienced) male dancers several times. This is one topic that is not discussed enough. However, I believe it comes down to one fact. As I said above, the male dancer is human, and the male body reacts in many ways, one of which is an erection. Accept it! Don't worry about hiding it, people will understand! You work hard to develop your dancer's body -- be proud of it.
Dance belts do vary in many different ways. In my opinion, the most important part is "comfort." You can get "binders" -- some dancers make them for themselves. But don't get carried away. Dance with the dancebelt that makes you most comfortable.[/i]