The Wisconsin Virtual Academy has grown in its four years to about 850 students, all there by choice. The online public charter school gets good results on state tests, equivalent to small-town districts from which it draws students. Parents rave about it.

So, naturally, the state’s biggest teachers union got a court to order it closed. If you wonder why, that just shows what you don’t know about schools, you amateur.

“My daughter has the most wonderful, hardest-working teachers in the world working for her,” says one parent, Julie Thompson of Cross Plains, near Madison. Her seventh-grader logs on with software made for virtual schooling. She goes to a virtual class with a live teacher. She has lessons assigned for her by a teacher. She does one-on-one work with a teacher. She gets her homework evaluated by a teacher, or she talks on a phone or meets face to face with a teacher. Notice who’s central to this.

Why, it’s the child’s parents, claims the union. The Wisconsin Education Association Council has been suing the school since it opened, claiming it breaks Wisconsin’s laws on teacher licenses. The union started by suing the state Department of Public Instruction which, being a union protectorate, switched sides. Make us stop funding the place, the educrats told an appeals court. Last week, the court agreed.

Mind you, nobody says the place does poorly. “They meet the state standard,” conceded the state’s lawyer — 92% of the students score advanced or proficient in reading. That’s beside the point, he told the court. Because parents help when children are stuck or act as an on-hand coach, they’re the teachers. Such parents are “unlicensed, untrained, unqualified and, um, adults who are not required to prove competence,” the state’s lawyer said, though he later said the state wants these incompetent peasants involved in schools anyhow. Maybe they can show up with juice boxes or something.

Siding with this, the appeals judges acknowledged it could absurdly make every teacher’s aide illegal statewide. Still, the law is the law, said the judges, and it’s up to regulators to decide how to enforce it. The Department of Public Instruction had convened experts to suggest how to accommodate such schools. It ignored their recommendations and it offered the academy no means by which it could regain legal grace.

That’s unprecedented, says Susan Patrick, who heads the North American Council for Online Learning. Of the 173 virtual schools educating 92,000 students in 18 states, not one has been closed because a court said online learning breaks licensing laws. “Wisconsin is kind of unique,” she says.

If Wisconsin Virtual Academy doesn’t win on appeal to the state Supreme Court, it’ll be a grim first and probably not last. The case puts Wisconsin’s dozen or so other virtual schools on thin ice — not to mention the 20 union members who teach at the school.

Why would the union do this? Because virtual schools are apparently taking education where it doesn’t want to go. For one thing, the union doesn’t seem to like alternative paths into teaching. Teach for America, which recruits top students from other fields, isn’t in Wisconsin, for instance. WEAC may well fear for its prerogatives.

Nor can it bear to see success for a kind of school that thrives with about one teacher to 42 students. For years the union has been pushing to add teachers by cutting such ratios. With enrollment now falling in about six of 10 districts here, any move to make teachers more productive, as virtual schools do, would deprive the union of the rising membership and influence it wants.

When the Legislature in 2006 changed the law to accommodate virtual schools, the union opposed it. So did the Department of Public Instruction, saying it would lower standards. Recall, the same department argued that it’s irrelevant whether Wisconsin Virtual Academy teaches well. Anyway, Governor Doyle, perennially backed by the teachers union, vetoed the reform.

This is the union, and officials beholden to it, in action, squashing a whole branch of school innovation. A fifth of students nationwide will take an online class in college. Michigan now requires all children to take at least one online class. In Wisconsin, already a hotbed of school choice, the teachers union and the education apparat apparently have had about enough of the educational marketplace that such online learning enables.

It’s telling that after I wrote about this in Wisconsin, I heard from union supporters saying that parents who choose virtual schools just don’t understand the value of making their children learn in lockstep with a room of random peers. Others said they fear online schools would appeal to parents who’d let their kids slide by, unlearning. This seems funny coming from an organization that’s never sued to close a brick-and-mortar school where kids really do pass through untouched by literacy. But it speaks to a real suspicion of granting discretion to parents.

That bit about unlicensed, untrained, unqualified, and incompetent wasn’t just lawyer talk. Some portion of the people running education in Wisconsin — and the nation, I’d guess — really views parents primarily that way. It could explain why charter schools face such resistance.

This makes the many teachers and principals who see parents as customers, not mere juice suppliers, that much more valuable. In Wisconsin, at least, you can’t count on that attitude to prevail.

Mr. McIlheran is a columnist for the Milwaukee Journal Sentinel.