Vouchers should be used to end the entrapment of poor children in schools that do not serve them well. It is a civil rights issue. If the trend toward neighborhood schools continues, then we will need school choice programs, vouchers among them, to prevent entrapment. The danger is not merely resegregation, although that is a valid concern. It is teacher stratification.
Most teachers unions insist on voluntary transfers based on seniority.
The poorer and less white a school gets, the faster teachers with seniority bail out. Eventually you get the educationally lethal combination of poverty, racial segregation, and teachers who are either rookies, ineffective or burned out. Parents deserve the opportunity to get their kids out of schools like that. The biggest mistake liberals make is assuming that vouchers are intended for people who want to send children to elite private schools. The people who most want vouchers want to send their kids to parochial schools and small private schools yet to be born.