The contributor of this essay (Letter from a teacher #17: scroll to find it; their URL system sucks), argues that vouchers are really just another Big Gummint game. 'Soft Statism', if you like.
There is a Milwaukee-area private school (non-denominational) which will NEVER, under any circumstances, accept vouchers. That was the word I got when the TT initiative was just getting off the ground, politically. And what Cato (and the essayist) mention are precisely the reasons that school will not get involved in the voucher system.
While it is true that MPS and a few other Wisconsin systems are just awful, it is ALSO true that the real enemies of "educating chilluns" are not the administrators, nor the teachers: the enemies are derelict parents--or more accurately, criminally delinquent parents. (It is also true that the administration, the State bureaucracy, and the teachers have been un-helpful in many regards and sometimes downright inimical to any sort of progress.)
However, those parents are products of Leftist/Planned Parenthood doctrines, specifically free love/free sex which Moynihan warned about, strenuously and to no avail. The essayist quotes the right apocryphal dictum:
That, my friends, is what we call "Root-Cause Analysis."
Meantime, Statism marches on in Wisconsin. Is that really a "credit" in Tommy Thompson's legacy?