I don’t know if the kid will be beat up, at 3rd grade they’d just think it was weird and he/she would probably end up being more isolated.
It is ridiculous that a child that age would have any idea about being a boy or a girl. Heck, my son thought he was Batman for a year and then became a cowboy. Instead of the kids in school getting counseling it sounds like the parents and the child need it.
At the time, my father was a head psychologist with Focus On The Family (a terrific group of people, by the way) and he was able to help walk me through the problem. God rest his soul, I don't know what would have happened without his guidence.
Kids who have this problem have to be dealt with almost exactly the opposite of how this kid's being dealt with.