MONTREAL — A school board north of Montreal wants a tribunal to levy a $15,000 fine against an entire school staff for intimidating their principal.

The legal action is the latest escalation in a four-year dispute at Sainte-Anne elementary school in Mirabel, Que., about 40 km north of Montreal.

The situation became so poisonous that the principal resigned amid allegations that teachers conspired to give her the silent treatment.

The school board says the 26 teachers sought "revenge" against Sophie Young and it is seeking moral and exemplary damages from the instructors and their union.

The grievance was filed in December before an education arbitration tribunal.

The teachers had accused Young of failing to follow up on student files while promoting an all-around lax atmosphere. They complained to the school board and when nothing was done, they held a rally at her office.

Five teachers quit at the end of the 2010-11 school year.

Parents got involved in September when teachers refused to meet with the principal.

A month later, on Nov. 24, 2011, 20 parents came to a general meeting at the school to demand Young's resignation. She immediately agreed to quit.

"Everyone was happy to hear that, but no one broke out the champagne," said teachers' union president Jean Dumais. "We were just relieved to move on."

A month later, just before the Christmas break, the 26 teachers at the school received a complaint from the board, demanding they pay $15,000.

The board also asked the union to pay for a mediator who showed up at the school in November but was unable to do her job when teachers refused to meet with her.

"This is a blatant act of intimidation on the part of teachers at Sainte-Anne school in retaliation against the principal," said the complaint. "We ask that the teachers union recognize that ... gathering en masse at the principal's office was an act of intimidation."

The union president said the complaint is a case of overkill.

"It's ridiculous," said Dumais. "I've never seen anything like it in my career.

"Teachers never intimidated Ms. Young. We're not talking here about a union of thugs."

School board spokesman Remy Tremblay refused to comment on the case, saying only: "All that we hope is that our grievance will be heard as quickly as possible."

The teachers and the union plan to hold a rally at the school board offices.