We have an implied social contract that disabled/disturbed kids get extra per-capita resources in public schools. If you cherry-pick the cheapest-to-educate kids away with vouchers at private schools, the public schools will become dumping grounds.

I would therefore support a voucher program where all the schools accepted all kids, or the "excluding" schools paid back some of the voucher money to schools that would take the difficult/expensive kids.

BTW, this whole debate is talked about as if its public education versus "choice" - really it's about teacher's unions versus subsidizing religious indoctrination. Nobody smells too good here IMO.