The teachers' union of the Lester B.Pearson School Board is fighting the board to get it to cut down the size of their classes, which they say are violating the terms of their collective agreement.

John Donnelly, head of the teachers' union, said the breaking point came during the last school year when the number of classes that went over the allowed student limit tripled, from 300 to 900.

"So at that point we decided this couldn't continue," Donnelly told CJAD 800 News.

"For the last at least ten years the board has been exceeding class sizes with generally no reason to do it."

Classes that are supposed to have 18-22 students would go over by 1 to as many as 12 students, most of them special needs students, so even one student can add on to an already heavy workload, Donnelly said.

"We would maintain a cause for teacher burnout," Donnelly argued.

"There are many young teachers who are put in a position of having to teach these oversized classes and it is a stress and a strain."

Donnelly said if the board insists on packing more special needs students into their classrooms, then they need more teachers and resources to handle it. Or, Donnelly said, they could transfer students into another school in the same jurisdiction.

A labour arbitrator is expected to rule next month. The board would not comment before then.