I amn't going to be bound by conventional grammar

My son Sam, who's six at this writing, started saying something and I corrected his grammar until I thought about it. The thing is, I think he's right.

Consider:

They aren't
We aren't
You aren't
He/she isn't

What should be rule be for "I am not"? Logically, it should be

I amn't

Obviously, if not the preferred contraction, it should at least be acceptable. So I've started using it in conversation. Join me. Repeat to yourself,