It helps kids express their personality. That should be left up to the kids and their parents. At my school, we’re allowed to dye our hair any color we want. We even have a “Crazy Hair Day” during Spirit Week. It’s important to be able to express yourself, so why can’t you express yourself at school?
I don’t think dyed hair is distracting. Most people would look at a kid’s brightly colored hair for a minute and then go back to what they were doing. plus the only reason adults say it is distracting is that they don’t like it.