Tuesday's back-to-school routine was disrupted for nearly 50,000 students by more than 2,500 teachers on strike in Pennsylvania, Illinois, Michigan and Louisiana.

Michigan had two strikes. All 33 teachers walked out of Baraga schools in the Upper Peninsula District Friday, shutting classes for 653 students, and a strike by Stock-bridge's 104 teachers began Aug. 30, affecting 1,893 students in the central lower Michigan district.Pennsylvania's strikes grew to seven over the weekend when the 315 teachers in the Cheltenham District of Montgomery County, with 3,800 students, reached an impasse in talks on salary and working conditions.

In southern Illinois, about 450 teachers in the Granite City school district, with 8,300 students, vowed to walk picket lines Tuesday.

In Abbeville, La., about 450 teachers, as well as schoolbus drivers and cafeteria workers, began a second week on strike.