Today is the last time the Hillsborough County School Board will gather before the Thanksgiving break, but the usual pre-holiday vibe may be muted in a district that has fallen on anxious times.Hundreds of teachers are expected to show up in protest over an ongoing pay dispute. Members of the teachers union voted last week to "work the contract" the week after Thanksgiving, meaning they will not perform tasks such as grading papers that they often complete on their own time. The meeting also follows demonstrations last week by hundreds of Hillsborough high school students who said they stood in solidarity with the teachers.Meanwhile, contract negotiations between the union the district administrators continue with no resolution in sight. Also today, board members are expected to choose a new chair, a task that two years ago resulted in controversy when a majority passed over long-time member Doretha Edgecomb. In addition, they will consider approval of four new charter schools that eventually could serve up to 4,400 students. They also would further strain the districtís budget, since charters take money that would otherwise go to regular public schools.The tensions over pay surfaced in late October when the district told union negotiators that it could not afford to give $4,000 raises that were scheduled for roughly a third of the districtís 14,000 teachers.Under a pay plan enacted in 2013, salaries remain the same for three years, then increase in the fourth year if the teacher maintains at least a satisfactory annual rating. But the district has been trying for two years to dig out of a financial hole that has left it with reserve accounts that are too small, a school maintenance backlog that is too long, and, now, a teacher pay plan that officials say is too expensive.District officials argue that employee pay has risen for the last four years and that Hillsborough teachers are the second-highest paid in the Tampa Bay area.The teachers union contends the district is obligated to honor its pay plan, and that district officials could make that happen with better money management.The School Board meets beginning at 3 p.m. at district headquarters, 901 E Kennedy Blvd. in Tampa.