What began as an experiment to create innovation through charter schools has become a movement to privatize public education, according to a new report.

Stan Salett, the study's co-author, spent more than four decades in public education and helped launch the nation's Head Start and Upward Bound programs. He says in the past two decades, a small group of billionaires – including News Corporation's Rupert Murdoch, who once called public schools an "untapped 500-billion-dollar sector" – have worked to assert private control over public education to make money.

"And that's what's at play now. You've got a lot of money on one side going in to create a privatized school system that becomes part of the new marketplace for hedge funds and Wall Street investors."

The Independent Media Institute study found 40 percent of the nation's 67-hundred charter schools are part of corporate chains or franchises. Salett says many charters do good work, and are operated by and accountable to their communities. But the report recommends a national moratorium on their rapid growth until the industry’s governing structures and business models can be assessed and improved.