A New York City charter school run by the highly-regarded KIPP network is bracing for a fight over the desire of many of its teachers to unionize, reports the New York Times. Unionization would surely bring work rules that would constrain the school leadership’s ability to peretuate its successful KIPP model.

Charter schools were one of the earliest incarnations of the modern U.S. school choice movement. Enjoying somewhat greater autonomy but generally lower funding than conventional public schools, they were intended to bring to the field of education some of the benefits of free markets. Overall, they tend to perform a bit better and more efficiently than regular public schools, but do not show the more consistent or significant advantages that genuine education markets demonstrate over public school monopolies.

But charter schools have a bigger problem than not quite having what it takes to create a free education maketplace. The great danger of charter schooling is that it could well prove to be a Trojan horse for the expansion of the existing 90% government school monopoly. Charter schools not only draw students away from the existing independent school sector, some are themselves former private schools that have opted to come under the umbrella of government charter status out of financial expediency. If, after absorbing students from the truly independent private sector, charter schools then lose what little autonomy they currently have, it will lead to the expansion of the existing state school monopoly.

That has long seemed to me to be their most likely outcome, and recent events are doing nothing to brighten that dismal prognosis. States and policymakers who want to innoculate themselves against the risk of charter schools gutting the independent sector while expanding the state school monopoly should adopt policies like education tax credits that give families easier access to truly independent schools.