I'm sorry, but I don't think I need to explain that self-expression goes beyond just hair and accessories and backpacks? Clothing itself is the main way of individualising your appearance on a daily basis, we really don't need to pretend that that isn't the case. Having to work around that isn't impossible, but it's 100% a huge restriction. My punk friend without his handmade clothing would've been much less "him". He ended up taking his apprenticeship at a tailor's btw, the craft was formative to him. And all of those work-arounds are assuming that it's even allowed or that alternatives are given, from everything I've ever heard people talk about uniforms those rules can get pretty damn strict. About non-clothing too. A uniform IS heavily restricting self-expression, that's just a fact, there's no way to talk around that. And "after school" is a silly argument when this is specifically about at school, where kids spend 80% of their social life. The other problem I see, especially with trans boys, is that they usually have to rely very heavily on baggy clothing like oversized hoodies to hide chest/hips. This needs to be available and, again, allowed by the rules. With how many people talk about not even having been allowed to loosen their mandatory tie, I can hardly imagine he would've been allowed to wear a big ballooning hoodie. My friend also wasn't publicly out at the time (this would have been very dangerous in our particular area in the early 2010's), so justifying wearing the "wrong" uniform would've also been an added barrier. I mean yeah sure there might be some partial solutions, and some schools might be so lax about their rules and have so many different inclusive options that there's a solution for everything (barely sounds like a uniform anymore at that point tbh), but that's ... pretty unrealistic, on a large scale.