It is difficult and I think it’s worth acknowledging that it IS a difficult situation to navigate for a young teen!
Well, it’s clearly difficult for older men too and they could do with some training on how to behave, but that’s another conversation, grrr.
Bringing up the new generation involves helping them navigate all this stuff, and I’m like you, a single mum of a boy, and very much ‘on it’ with regards to sexism and equality. But it’s hard to instil these values in a society which seems determined to move backwards not forwards in this regards.
Anyway, I’d have an open discussion with him about why the girls are dressing like this. Covering experimenting with fashion and body image and their own sexuality and the way they can impact on the world. I’d dwell on the idea that it’s internally driven for them, not externally motivated ie they are not doing it FOR him, and he shouldn’t take it as a signal about how available they are or what they might be open to letting men and boys do to them etc etc etc.
Then I’d help him come up with ideas for how to behave around his friends who are wearing scanty clothing, and what not to do.
It’s always good to make a few jokes here and use someone else as an example, perhaps an imaginary idiotic person (or real life people you both know who might do socially cringeworthy awful things at a push... enough to be used as props in your story making anyway!
Then throw in a few ridiculous and extreme reactions and stuff... like the guy who tries so hard not to look at his friend with the revealing top and shorts on, that he ignores her and keeps turning his back on her the whole time, and she ends up slapping him and storming out. Or the borish pig who is so busy staring at the girls bottom that he doesn’t look where he’s going and ends up falling down a man hole, where he gets left as his friends decide to walk off without him.
It’s good to use extreme examples because he probably does know more than he thinks about how to behave, it’s just about feeling confident enough. With ridiculous examples of other people clearly getting it wrong, he can gain in confidence as he can identify how wrong they are and what not to do, so he must have some sense of what makes a good friend to girls experimenting with their look.
And I’d give him a get out so he can remove himself from situations he’s uncomfortable with or just finds too much to deal with.
You know your ds so you have to pitch this stuff at a level he can understand, but I think that’s how I’d handle it.
It’s hard if your son has hit puberty in the same way yet, so might be baffled by it all at the moment... or maybe he’s battling raging hormones himself and everything is just weird and unreliable and nothing goes by the same old rules anymore, inside or out!
I’d also point out that all this is probably a phase so by the time autumn hits fashion desires may have all moved on anyway.
Finally, I’d point out that it’s worth keeping it in perspective. How much time does he spend looking at his male friends shirts? Probably all of a few seconds. Because it’s just not that important or interesting. And when he’s feeling comfortable around his female friends again, it will be the same (or similar anyway). Because, it’s not their chests that are the interesting thing about them...