PHILADELPHIA, April 17 — In what is believed to be the largest experiment in privatization mounted by an American school district, a state panel charged with improving the Philadelphia public school system voted tonight to transfer control of 42 failing city schools to seven outside managers, including Edison Schools Inc. and two universities. The three members of the School Reform Commission appointed by Gov. Mark Schweiker voted for the plan, while the two members appointed by Mayor John F. Street voted against it. The vote capped a fiery three-hour meeting in which the two sides had split over whether Edison,...