A-religious endeavors are not inherently atheist. Public education is certainly not atheist.
Vouchers as a whole should be eliminated. Giving public funds to private schools is nothing short of evil. Using children as a pawn to move that money doesn't change anything.
Ultimately these schools exist to completely bypass any standards of education. That includes teaching religion, which is not allowed in public schools for good reason. This, on its own, isn't awful. But combined with stealing money from public schools it's a huge problem.