This is a school, they don't have to follow the wider rules of society. In the normal world, disrespecting a superior won't see you punished, but in school you can be punished very severely. Similarly, in the regular world, cross dressing is fine, but in school, if its against the rules for a boy to wear a dress then its against the rules. It sounds to me like this kid was a repeat offender and this was the straw that broke the camel's back. Its not disgraceful, its not a terrible injustice, its a little unfair, but come on, don't do the crime if you can't do the time. School rules are different to the outside world because its a different environment altogether and needs to be controlled as such, they should be followed unless they're ridiculously unreasonable and this clearly isn't that unreasonable.