He choose to grow his hair out. He can choose when he wants to cut it.
It's as easy as that.
As a parent I've let him make this decision.
So often I get rude comments, mostly from older ladies at the grocery store that say "That kid needs a haircut."
More often he gets mistaken for a girl.
But he doesn't care. He makes sure to tell people he's a boy. At school most the other kids and parents know him because of his hair.
Here's his view on the long hair
See I can pat myself on the back for being a good parent so shove it.