Classes in British Columbia weren't in session Monday as thousands of teachers began a three-day strike over wages and benefits.

About 41,000 of the province's teachers are estimated to have walked off the job, leaving many parents scrambling to find childcare.

Some B.C. public schools remained open but administrators warned ahead of time that there wouldn't be enough support staff on hand to adequately supervise students.

The teachers aren't allowed to set up picket lines or demonstrate outside schools but remained nearby, handing out leaflets and trying to engage the public.

Classroom safety and wages are among the more contentious issues up for discussion.

The teachers are asking for a 15 per cent pay increase over three years, a demand that the province insists it cannot afford without carving benefits out of the existing contract.

As well, B.C.'s Liberal government is adhering to a "net zero" wage freeze for all public sector employees, noted CTV British Columbia reporter Brent Shearer.

According to Susan Lambert, president of the BC Teachers' Federation, the net zero policy applies to more than just wages.

"Every aspect of the employment relationship is hit by the net zero mandate, so we can't bargain anything," she told CTV News Channel on Monday.

The size and composition of classes has also been a major sticking point in negotiations.

Class sizes have steadily increased to about 30 children for a high school or middle school setting, Shearer told News Channel on Monday.

He added that large numbers aren't usually a problem for advanced students; it's needier kids who typically don't thrive in bigger classes.

"The teachers are complaining that there's less support staff for children with special needs," said Shearer.

The province's teachers have been on limited job action since September, but because the profession is an essential service in British Columbia, that strike was restricted to administrative tasks such as not marking exams or completing report cards.

B.C.'s Labour Relations Board approved the three-day strike last week after discussions between the teachers' union and the government reached an impasse. The teachers can walk off the job legally for three days and afterwards are only permitted to strike one day a week.

Lambert said the teachers and the government have been at the table for more than a year and have explored the possibility of mediation or arbitration.

The strike was announced on the same day the province planned to debate back-to-work legislation, which could have ended the strike and limited job action.

"Once it passes, the strike will be essentially illegal and any teachers who do continue to strike will be hit with a $475-a-day fine, $1.3 million a day for the union," said Shearer.

Bill 22, the Education Improvement Act, also extends the current contract and would appoint a mediator to draft a list of recommendations.

For her part, Lambert anticipates even more acrimony if Bill 22 passes.

"It's something that, I think, will mean continued protests," she said.