Me vs. all that is cool

What would you do about this? I've written here before that there are artists I won't let my kids listen to, because I don't think their songs are appropriate for kids. Not to say they should be censored or banned or forced to write about the moon in June, just that children and young teens don't need to be listening to that stuff, at least not in my house. So now: My son has been reporting that in his middle-school art class, which is a self-contained cycle class but is led by an art teacher who is not a special educator, the teacher plays Green Day CDs. That's bothered me some; I'm sure she's a Green Day fan, and I like their music too, but I've looked up their lyrics and a lot of them are -- as befits an adult act -- political or provocative or worded in a way that, again, isn't appropriate for kids. And then: The last couple of days, my son has reported that they get to use the computer to do whatever they want in art class, and they've been going to 50cent.com (home to another artist I've nixed) which, his friend promptly added, has pictures of barely-dressed women. Now, I went to the site, and I couldn't find the women (probably because I don't have the same motivation as some of the boys in his class), but I did see right off the bat more guns than I want my kid looking at in art class, I'll tell you.

But what do I do? Can I really storm into that art class like Tipper Gore and tell this woman to stop polluting the mind of my boy with her mature music and her dangerous websites? I'll feel like a bat out of the '50s. I know I can't control everything my kids see and hear, but should they be hearing and seeing this stuff in school, in class? Do I have a legitimate beef? I fear I'm going to be taking on the "cool teacher" here. There's a reason it's called "Parenting Isn't Pretty."