Why should boys have rules about their hair, why should there be rules about colour of hair or girls with straight hair have to tie it up?
Why indeed? Provided it's safe and doesn't get in the way of learning, what does it matter what colour it is, how short or long it is, or whether it's up or down?
Or are you saying that rules are only a problem if applied to a black child?
I'm saying that rules are a problem when they are (a) stupid and (b) racist.
I do enjoy the way people who are in love with rules are outraged at the concept that they should comply with the country's rules as set out in the laws of the land.