It's the same here in North Carolina - school attendance isn't required until age 6. I think it's because a child's level of maturity and readiness is an individual thing that can't be set by law.
It looks like your problem is actually with your child's mother. When you constantly fight her over every issue (I've seen your other posts) you are not only hurting her, but you are also creating stress and anxiety in your child's life. You need to find a good attorney to handle this for you. I don't know about your state, but in our state you can get a free moderator through the court system, but your situation may have gone beyond moderation.