This reeks of political child abuse; the parents wanted this.
One problem I suppose with the charter system the same as could happen with the proposal in Britain to encourage more groups of parents to start schools within our state system which a greater say over the ciriculum taught. the set up and how and what is taught is much freer and encouragement for religious bodies such as the Church of England to more involved and as long as the children sit and the majority pass crtical development/education tests and at various ages there is much less interference.
The problem I see with your Charter system and what we are just starting (in some cases have been running for a while) is that it is sadly open to abuse of what could be used to create a more balanced education than the normal public/state schools provide.