Philadelphia teacher strike is on, but not Chicago's

Chicago headed off a massive teacher strike Thursday, but negotiations in Philadelphia faltered and a state mediator was called in to resolve a walkout of 755 Pittsburgh-area educators.

The Chicago Teachers Union and the Chicago Board of Education reached a tentative agreement allowing classes to open on time Sept. 8. The talks were aimed at trying to work out contract concessions that would help the school board balance its budget. State law prohibits classrooms from opening if the budget isn't balanced.