Again, this has nothing to do with this situation because this boy does not have long hair because of his religon. All public schools have exceptions for religious customs, I'm sure this one is no different. This child is not wearing his hair long because his religion dictates it, he's wearing it long because his parent does. It is this parent's choice to send him there being that pre-school is not mandatory. When a parent makes a choice to send their child to school, they make the choice to abide by the rules set by the school.
I understand exceptions however you can't say ok this boy can have long hair and this boy can't...it just doesn't work that way...