I am so sick of seeing this myth, stereotype, whatever you want to call it.
I have 2 boys, and they are plenty immature; I have lots of friends with girls who are just as immature as my boys if not more so in some ways.
I am tired of people saying boys need to be redshirted (meaning held back from Kindergarten another year if they turn 5 in the summer), I believe EVERY child is an individual and should not be grouped into some lump category based on gender.
My older son is 7 1/2 now and in 2nd grade. He started K at a young 5, he turned 5 two weeks before Kinder started. He had been in Prek for going on 3 yrs, he was in daycare and they start teaching at 2 1/2 or before.
He was ready so we sent him and he did great and still does great. He has been on the Honor Roll every grading period since K, is in the Accelerated Reader Program, he is very smart. ANd his teachers don't think he is any more immature than any of the other kids, boy or girl.
I just want to say, your child is an individual. Just because he's a boy doesn't mean he isn't ready for school.