Well, the school did overturn the decision. I've had a number of times over the years when I just wasn't sure about a given outfit. So I would send the kid up to the office to get the principal's opinion. Now I tend to let things slide unless it's egregious. I figure that's administration's job.
Many schools keep extra clothes (i.e. polo tops, khaki pants) on hand for a variety of reasons, not just dress code violations. I've heard of a few schools in low-income areas that have washers and dryers as well.
What if they catch you thinking about an adult female wearing a halter top? And it makes you smile really big, which makes some teacher or administrator suspicious and so you end up being confronted: "What were you thinking of?