Sen. Bernie Sanders will call for a federal ban on building for-profit charter schools in a major education policy address to be delivered Saturday in South Carolina, a senior campaign official for the 2020 presidential contender tells USA TODAY.

Additionally, Sanders will pledge to impose a moratorium on using taxpayer funds on charter school expansion in communities if he’s elected president, a position that the NAACP has been advocating.

The speech by Sanders comes one day after the 65th anniversary of the landmark Brown v. Board of Education ruling handed down by the Supreme Court, which ruled segregation in public schools to be illegal.

“Our school system can no longer put up fences for black and brown children,” Sanders said in an op-ed in the Asheville Citizen-Times, part of the USA TODAY Network, published Friday. “On this 65th anniversary of the Brown vs Board of Education decision, we are going to tear down those barriers and create an education system that works for all people, not just the wealthy and powerful.”

Charters are publicly funded but privately run, and have grown in popularity around the country since their inception more than 25 years ago. Advocates say their relative independence – they face fewer instructional and bureaucratic regulations, and are largely free from collective bargaining – allow educators to innovate.

Charters can be run by for-profit or non-profit companies; the vast majority are run by nonprofits.

Response from charter school advocates

Advocates for charter schools blasted the Sanders’ proposal.

“Sanders’ call is out of touch – as usual – with what African Americans want,” said Amy Wilkins, the senior vice president of advocacy for the National Alliance of Public Charter Schools. “More disturbing, the senator – for personal political gain – would literally lock African American students into schools that have failed them for generations.”

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Teachers unions around the U.S. have been pressing for local and federal lawmakers to stem the proliferation of charters, which they say are siphoning funding away from traditional public schools.

The NAACP, National Education Association and the American Federation of Teachers have also taken aim at charters for intensifying racial segregation in schools, as nearly 1 out of 5 charter schools have a 99% percent minority student body.

President Trump’s education secretary, Betsy DeVos, has been a longtime supporter of charter schools. DeVos, and her husband, Dick, the heir to the Amway fortune, have spent millions of dollars on behalf of the charter school movement in their home state of Michigan.

The speech by Sanders to address the role of charters comes as he tries to win over African American voters in the early-voting state of South Carolina.

Where the rest of the field stands

The move to target charters by Sanders also offers an opportunity for the senator to set himself apart from former Vice President Joe Biden, the Democratic presidential frontrunner, with a message that will likely resonate with teachers union members.

During his time in the White House, President Obama was supportive of merit pay and charter schools, both issues generally opposed by teachers unions. The Obama administration’s education reform effort, dubbed “Race to the Top”, gave states a chance to compete for federal grant money if they adopted a series of reforms, including link student performance to teacher evaluations. Biden’s brother, Frank Biden, is also a former executive in a company that developed charter schools.

Other Democratic contenders also have backed school choice in the past.

Before winning a U.S. senate seat, Cory Booker was a fierce advocate of charters during his time as mayor in Newark. A third of Newark’s students now attend charter schools. The New Jersey city’s charters are among the highest-performing the in the country, according to Stanford University’s Center for Research on Education Outcomes.

Sanders is also expected to call for mandating that charter schools comply with the same oversight requirements as public schools, establishing rules that require at least half of all charter school boards are teachers and parents, and codifying that charters disclose student attrition rates, non-public funding sources, and financial interests of the charter network.

The Vermont senator is the first major 2020 Democratic candidate to call for a ban on for-profit charters or a moratorium on funding the expansion of charters.

Nearly 3.2 million students, roughly 6% of all public school students, attended nearly 7,000 charter schools nationwide last school year. Enrollment was up 5 percent from the previous year, according to the National Alliance for Public Charter Schools

Contributing: Erin Richards