Milton Friedman is most widely known and celebrated for his monetary policy. But school choice – making markets work for parents and students – was one of his most passionate priorities. Friedman’s critical insight has been redirecting debate from one of mandates versus markets, to making markets work – especially for people locked out of markets by poverty, monopoly and constricted supply.

School choice has earned its largest, longest experiment in Milwaukee, Wis. Eighteen thousand children attend independent and religious schools financed by the education vouchers Friedman advocated for half a century. Another 10,000 attend charter schools independent of Milwaukee Public Schools, and over 8,000 Milwaukee students enroll in school districts outside the City of Milwaukee.

But tens of thousands of Milwaukee choice students are not the biggest story. The greatest surprise has been how Milwaukee Public Schools has responded to the challenge and competition from vouchers, charters and suburban schools. Fifteen years into Milwaukee’s school choice experiment, more than half of Milwaukee Public School’s 90,000 students attend schools that did not exist in their current format when school choice started.

Schools offering effective programs have thrived and grown. Milwaukee Public Schools, which reduced options for low-income, central city and minority families for decades, expanded both neighborhood school options and specialty schools previously targeted to middle class and white enrollments. International Baccalaureate, Montessori, and other popular specialties have been replicated in both Milwaukee Public Schools and the choice and charter sectors.

Milwaukee has redefined "public education" from a government monopoly to a multi-sector public service delivered by governmental, independent and religious schools. Parents know, or learn fast, which schools work and which schools don’t.

Best of all, terrible, persistently failing schools have closed. Middle schools for sixth- through eighth-graders — an often bad idea in general, with disastrous results in many urban low-income communities — have closed and been replaced by smaller, safer kindergarten through eighth-grade schools. Three low-performing high schools have been shut down and converted to multiplex facilities for smaller, more responsive academies. Milwaukee public elementary schools that cannot sustain their enrollment are closed and no longer drain the system of resources.

Mr. Friedman died on Nov. 16, 2006. In the last 10 years of his life, he concentrated on promoting educational freedom through school choice, including founding the Milton and Rose D. Friedman Foundation with his wife.

The market Friedman envisioned works. Remarkably, school choice works not only for students, families, and independent and religious schools, but for Milwaukee Public Schools.

John Gardner is a self-described left-wing Democratic organizer, with 40 years’ experience with labor unions, cooperatives, election, and schools. He has come to believe that markets constitute one essential form of democratic power, essential to "democracy’s three essential values of liberty, equality and community."