Well, I wasn't expecting this to get nearly so much traffic.
I actually agree wholeheartedly that the tastes of teenage girls are horribly shaped by hideously misogynistic porn culture (in the way ALL out tastes are shaped by our context). I wish this were different, and I would choose different clothes for my daughter, if I was in charge. But at 16, I choose to discuss and debate this stuff with her rather than to attempt to control it. She gets that choice, because it is her body, and she is a highly intelligent, head-strong, thoughtful human being I respect enormously. There plenty of areas in which I step in, but this is not one of them.
And it's also complicated. Involved in this situation is the body shaming of the well-endowed, the implication that women's clothes should be chosen with men's eyes in mind (in either "direction"), and the all ways the teacher's tastes and approaches have also been shaped by our misogynistic culture. I have no intention of complaining, btw, because she will have meant well on some level, and because DD wouldn't want me to, but thank you very much to those who've understood why the comment was problematic.
I don't think the lines between "sexual body part" and "non-sexual body part" (smiling is a potentially sexual act; breasts are primarily for feeding babies), between "acceptable" and "unacceptable", or "work wear" and "not work wear" are anywhere near as cut and dried as it seems some people here do, and that's surprised me, but it's been interesting.
Anyway - thanks again for the perspectives on this. Hope everyone has a lovely bank holiday.