Union President Melissa Ravas said working two years without a contract warranted the cancellation of the first day of classes.
"Our teachers are frustrated," she said. "Obviously, we would all rather be in our classrooms this morning but when we met (Monday, with district negotiators), the district came up empty-handed. It was clear we were more interested in preventing a strike than they were."
The 380 teachers plan to picket at the district's administrative building in Shaler, Pa., until district officials bend on issues ranging from salaries to healthcare contributions, Ravas said.
The teachers have worked without a contract since August 2011, the Pittsburgh Tribune-Review reported.
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