Forty-two of the city's low-performing middle and elementary schools are to be turned over to for-profit companies and universities as part of the nation's largest school privatization plan.

The School Reform Commission, created by the state after it seized control of the city's public school system in December, voted 3-2 Wednesday in favor of the plan, which affects more than one-quarter of the city's schools and thousands of children.

The decision turns over 20 schools to a for-profit company, Edison Schools Inc. Twenty-two others will be turned over to other private companies and non-profits, and 28 more will be run by parent groups. The commission already had voted to make Edison the lead consultant in district-wide reforms.

The changes could be in place by September. No high schools would be handed over to private entities.

The decision came over the objections of unions, students and some parents who argue that companies like Edison have an unproven track record.

"I am greatly concerned that the magnitude of the change being proposed is too ambitious at this point," commissioner Michael Masch said. Commissioner Sandra Dungee Glenn said Edison had "a mixed record of performance at best," and should be given a more limited role.

Those concerns were overridden by the three commissioners appointed by Gov. Mark Schweiker -- Edison's biggest backer in Pennsylvania. Mayor John F. Street, who appointed the two dissenting commission members, said he accepted the decision.

Daniel Whelan, a school reform commissioner, said the schools are in immediate need of aggressive reform. "If anything, we erred on the side of caution," he said.

Other large cities have experimented with privatization by turning over small numbers of schools to private managers, but none on as large a scale as in Philadelphia.

About two dozen students spent the night before the vote camped outside the city's school administration building, then formed a human chain across its wrought-iron gate and refused to allow anyone inside.

Andrew Hopkins, a 16-year-old student at Simon Gratz High School, said he was willing to go to jail.

"It's worth it. We are talking about our education here. They shouldn't be giving these schools to private companies that care mostly about their own profits," he said. "We want a parent vote in every school they want to take over."

The commission decided to postpone the meeting for two hours and move it to another building several blocks away rather than make a forced entry.

After the vote, commission chairman James Nevels called it "a historic day" for the school system, the nation's seventh largest, with 200,000 students in 265 schools and a $1.7 billion annual budget.

The system's new private partners will be moving into schools where 80 percent of the students qualify for free or reduced-cost meals and more than half score in the bottom quarter on state reading and math tests.

The commission said it would bring in seven groups to operate 42 schools. Besides Edison, the for-profit companies Chancellor Beacon Academies would run five school and Victory Schools would run three.

Three of the city's biggest universities -- Temple, the University of Pennsylvania and Drexel -- would get a share of 12 schools. Universal Cos. would run two schools.

Edison Schools feature a longer day and school year, a heavy investment in technology and intensive staff development. The company runs 136 schools in 23 states.