On registration day for our students, I got my first taste of being a teacher in a gym full of high school students. It wasn't quite like I expected. For one thing, they weren't really all that loud for over a thousand people in one place. Also, I didn't have the same reaction as one teacher, who thought that none of the kids looked like they had put in any thought as to what they were going to wear on the first day of school. While no one was wearing formal wear or even dresses or nice pants, I'm sure many of them spent a lot of time agonizing over their carefully constructed "I just woke up and threw this on" look.
Some teachers are not surprisingly pro-uniform, although from what I've heard, many parents in our community are decidedly against the idea of their child being required to wear the same thing as every other student in the school. From what I remember of high school, I was never distracted by another student's hair/clothing/jewelry enough that I could not focus on the lesson. Also, being hormonally charged would not disappear just because the bodies were covered in uniform dress, although I do agree that parts hanging out would be disturbing and am glad that is prohibited.
I think the most important factor in how much a student will learn in any school is not what everyone is wearing, but rather what is being taught and how teachers are teaching it. Most everyone can probably think of at least one teacher in their school experience who was just so interesting that you couldn't help but learn something. I had several in high school - Coach Altizer - who taught history like he had lived it, Mr. Ramsey - who made geometry proofs entertaining, and Mrs. Ware - a giant personality trapped in a tiny body, who murdered our English papers, and cut us regularly with her wit. I hope to be that kind of teacher that students remember as being passionate about imparting knowledge and inspiring them to absorb that knowledge, seek their own ideas and continue to be involved in creating the future, however they choose to do so.