Yet another way charter schools work to manage their student load in ways actual public schools cannot: enforcing their own Kindergarten entry cut-off dates. Private schools do this too, officially or unofficially. I've been told that some local public schools strongly encourage their own cut-off dates to some parents, but even if that's true it's not something they can enforce.
That said, I'm still leery of the new Kindergarten entry cut-off points - especially as TK disappears, I don't see any evidence that the earlier cut-off will lead to more socially and academically ready students. I think they'll be bigger, but another year with nothing than more aging is not a panacea to Kindergarten readiness.