A Wisconsin court rejected a high-profile lawsuit by the state's largest teachers' union last month seeking to close a public charter school that offers all its courses online on the ground that it violated state law by depending on parents rather than on certified teachers to educate children. The case is part of a national trend that goes well beyond virtual schooling: teachers' unions are turning to the courts to fight virtually any deviation from uniformity in public schools.

Unfortunately, this stance not only hinders efforts to provide more customized schooling for needy students, it is also relegating teachers to the sidelines of the national debate about expanding choice in public education.

Virtual charter schools grab headlines, but they are actually relatively minor players. The Center for Education Reform reports that there are 147 online-only charter schools in 18 states, with 65,354 students. In other words, virtual schools make up just 4 percent of the entire public charter school sector. And a third of them can be found in just one state, Ohio.

Still, they are valuable for many students. For example, a student in a rural community with few schooling options who finds the curriculum in her school too limiting might be better served through an online program that allows her to learn at her own pace. So, too, might a ninth grader who finds unbearable the jock-and-popularity culture that still largely prevails in our high schools. And some parents may want to be more involved in their child's education than is possible in traditional public schools but don't have the time or resources to do fully independent home schooling.

To be sure, virtual charter schools raise some accountability problems. The Electronic Classroom of Tomorrow, Ohio's largest virtual school, and two online charter schools in Florida ran into trouble recently for such practices as enrolling ineligible students. The schools clearly need better state regulation and oversight.

What they don't need is reflexive opposition from the teachers' unions. And virtual charter schools are just part of a larger debate about public education. There is a universal American desire for customization and variety in goods and services, and education must respond to that demand, whether the unions like it or not.

The two main issues, of course, are giving vouchers to students who switch to private schools and offering more choices through public schools in an effort to improve quality. While there are legitimate reasons to be skeptical of school vouchers as a remedy for our educational problems, it makes no sense for teachers' unions to continually fight against the idea of more choices for parents even within public education.

Public charter schools, in particular, are a worthy effort to provide non-standard students with non-standardized options. On average, charter schools are smaller than traditional public schools and often have longer school days and more intense curriculums; they also experiment with using instructors without traditional teacher training or having the teachers collectively manage the school themselves without a principal. This sort of variation should be welcomed, not tamped down.

America's teachers are ill served by the unions when policymakers and politicians are increasingly forced to work around them rather than with them; and the important contributions teachers' unions can make are lost. In an era of strained budgets and competing priorities, it is politically foolish for the unions to alienate parents and essentially encourage families to leave public schools.

This debate, like the ones over many other education issues, is fundamentally about who gets to have power. Yet the power the teachers' unions now wield will be fleeting if public schools do not become more responsive to parents.

An industry cannot survive by rushing to court every time a new idea threatens even a small slice of its market share. Instead, maintaining, and even broadening, support for public schools means embracing more diversity in how we provide public education and who provides it.