More than 100 high school teachers with the Upper Canada District School Board (UCDSB) received redundancy notices Tuesday in what their union is framing as a "direct result" of the province's proposal to increase class sizes.

The UCDSB covers a wide swath of eastern Ontario from Brockville to the Quebec border, and employs about 650 secondary school teachers.

The notices don't necessarily mean 100 teachers will lose their jobs, because some redundancies will likely be absorbed by retirements and voluntary departures.

Danny Thomas, district president of the Ontario Secondary School Teachers' Federation (OSSTF), blames the redundancies on the PC government's proposal to increase class sizes.

"Going from 22 [students] to one [teacher] to 28 to one in the student-teacher ratio, that could result in one in every four teachers in Ontario losing their job," Thomas said. "Teachers are going to be stretched even thinner to provide a high quality of education to the students."

But board chair John McAllister denied the class size proposal is behind the redundancies.

"That [government proposal] has had no impact on this round of redundancy notices whatsoever. It has no bearing on our calculations," he said.

Instead, McAllister blamed the redundancies largely on a serious student transportation deficit now facing the board. The UCDSB owes $20 million in retroactive payments to school bus companies stemming from a recent arbitrator's settlement.

"The board is bare to the bone, and the settlement is hanging over our heads," McAllister said. "We have an obligation to be fiscally responsible."

Thomas, who taught with the UCDSB for 17 years, said he's "fully aware" of the arbitrator's ruling.

"But I believe Ford's cuts play in role in this as well," he said.

The UCDSB must pass its budget by the end of June.