Even ardent opponents of school choice accept that parents have the right to send their children to private schools. That may soon change in New York state, where education officials are preparing new guidelines to impose strict regulations on the instruction that religious and other private schools provide, while empowering local school districts to shutter those schools if they fail to meet state standards. The plan is not only ill-advised, it may end up costing the state billions in annual school aid to nonpublic schools.

Parents...