Democratic presidential candidate Bernie Sanders spoke out against charter schools on the campaign trail earlier this month, at a town hall in Newmarket, N.H.

"I'm not in favor of privately-run charter schools," Sanders said to applause at the Jan. 3 event. "If we are going to have a strong democracy and be competitive globally, we need the best educated people in the world. And I believe in public education. I went to public schools my whole life. I think rather than give tax breaks to billionaires, I think we invest in teachers and we invest in public education."

"I graduated from a charter school in New Hampshire," the questioner said. "The funding for it was always being cut. We had to fire our janitor. We had to move several times just to be able to survive. I'm wondering how your funding would be for public schools and charter schools as well."

It's not clear exactly what Sanders meant by "privately-run" charter schools. All charter schools are run by non-governmental organizations. Most are run by non-profit groups, though some are run by for-profits. Perhaps Sanders opposes all charter schools, or just the for-profit ones.

The Sanders campaign did not respond to a request for clarification.

The National Alliance for Public Charter Schools responded to Sanders's comment in a statement provided to the Washington Examiner. "We would like to point out to Sen. Sanders that charter schools are public schools," said Nina Rees, the group's president and CEO. "Like Mr. Sanders, we advocate for high-quality public education, and therefore seek to grow the number of high-performing charter public schools across the country. Research has demonstrated that low-income students in charter public schools gained 14 additional days of learning in reading and 22 days of learning in math per year."

Charter schools are publicly-funded and do not charge tuition. Compared to traditional public schools, charter schools have more independence in their operations and curricula, which is why so many families find charter schools desirable. They are open to all students, but they often don't have enough space to meet demand. In that case, they use a random lottery system to determine admission.

Hillary Clinton, Sanders's rival for the Democratic nomination, has her own strange history with charter schools. Clinton was supportive of charter schools in the 1990s. As a senator and secretary of state, she was largely silent on the issue. Then, in Nov. 2015, Clinton went negative: "Most charter schools, they don't take the hardest-to-teach kids," she said in an interview. In December, Clinton praised the law replacing No Child Left Behind, partially for aiding charter schools. "The legislation," Clinton said, "also authorizes critical resources to … expand high-quality public charter schools."

Jason Russell is a commentary writer for the Washington Examiner.