1. Vouchers divert public resources from public to private schools, in essence subsidizing people who can afford private education at the expense of those who can't.
2. Vouchers segregate the K-12 school population. Vouchers were lobbied for by the Catholic Church for decades but morphed in Virginia after passage of the Civil Rights Act in an attempt to thwart integration. It took the courts to strike it down. That they have condoned it now is a disgrace and reflects how far right our judiciary has slithered and how much influence churches have gained over legislatures.
3. Charter schools were created as the intermediate life form between public schools and private schools to be financed with public money. As charters wither due to poor accountability, unaccountable voucher schools will replace them.
4. There are no normative standards for private schools. They traverse the spectrum from Ivy League prep academies (which won't be in the voucher business save as a tax deduction for wealthy parents) to little schools that have nothing but a Bible or a Koran for a text and revealed doctrine as a curriculum.
5. Private education for the masses is the road to democratic extinction and the Balkanization of the American people, something public schools were created to avoid.