I agree with Champ. My AD when I coached in NC made it clear, we were to always represent our school, and our sport to the utmost of respect. When coaching against a competitor, we were to never wear jeans and were to always wear at the very least a shirt with a collar with casual slacks There are so many ways to look nice when coaching without the jeans, t-shirt and all. Now for those who know me, they will tell you that I prefer jeans, even shorts and t's around the house and at play, but coaching as a profession should be represented as a profession, not a hobby or casual affair.
I will also say, that I have to admit, the standards are not quite as high for a kids tournament, weekend non school related tournament and so forth. I don't know if that is right, but I will say that even when coaching those tournaments, I try to make sure to present myself as a professional, which at the least means a shirt with a collar and a 'nice' pair of jeans. For school functions though, a totally different thing.