And if their long hair did provide a distraction to the learning environment, they WOULD be asked to cut their hair. But that is the whole point - the “litmus test” so to speak, is if it causes and interruption to the learning environment.
I don’t know about the school in question, or schools in your area, but around here - long hair does not even bring a second look - but a spiked mohawk would cause quite a stir - and not just for a few minutes - but for an extended time.
Another poster pointed out that they should put a dress on the boy.
Sounds about right.
Besides, these kids are in Kindergarten. How do they know what’s normal?