Well... at least that's what the teachers unions would like us to think. In The Wall Street Journal's review & outlook:

The Education Borg
January 23, 2006; Page A16

Teachers unions keep telling us they care deeply, profoundly, about poor children. But what they do, as opposed to what they say, is behave like the Borg, those destructive aliens in the Star Trek TV series who keep coming and coming until everyone is "assimilated."

We saw it in Florida this month when the state supreme court struck down a six-year-old voucher program after a union-led lawsuit. And now we're witnessing it in Milwaukee, where the nation's largest school choice program is under assault because Wisconsin Governor Jim Doyle refuses to lift the cap on the number of students who can participate.

...Mr. Doyle, a union-financed Democrat, has vetoed three attempts to loosen the state law that limits enrollment in the program to 15% of Milwaukee's public school enrollment. This cap, put in place in 1995 as part of a compromise with anti-choice lawmakers backed by the unions, wasn't an issue when only a handful of schools were participating. But the program has grown steadily to include 127 schools and more than 14,000 students today. Wisconsin officials expect the voucher program to exceed the 15% threshold next year, which means Mr. Doyle's schoolhouse-door act is about to have real consequences.

There's no question the program has been a boon to the city's underprivileged. A 2004 study of high school graduation rates by Jay Greene of the Manhattan Institute found that students using vouchers to attend Milwaukee's private schools had a graduation rate of 64%, versus 36% for their public school counterparts. Harvard's Caroline Hoxby has shown that Milwaukee public schools have raised their standards in the wake of voucher competition.