More than 8,000 students across Toronto may have to find another way to get to school on Thursday as their bus drivers weigh whether or not they'll get behind the wheel.

The Toronto District School Board and Toronto Catholic District School Board say they've received notice from Stock Transportation that drivers in two of the unionized divisions, north and east, will be in a legal strike position as of May 2.

"At this point in time, a strike is not guaranteed, however it it possible should an agreement not be reached by this date," TDSB spokesperson Ryan Bird said in a statement.

Negotiations are ongoing between Stock Transportation and its unions, the statement says.

A strike would affect approximately 4,105 students in the TDSB and 4,235 students across the TCDSB.

In a statement, Unifor says school bus drivers transport up to 70 children at a time and are often expected to perform unpaid tasks before, after and between their routes.

"This practice has become so widespread that driving a school bus is now partially volunteer work — instead of regular paid employment," said Unifor Local 4268 president Debbie Montgomery.

"I don't think this is a reasonable way to treat the people with whom we entrust our children. We endeavour to have each school bus driver paid for their working time."

For its part, Stock Transportation says it only received a proposal Friday evening and has been working over the weekend to review it, adding it won't comment publicly on the details of the negotiations.

"We certainly hope the union will give us time to review their proposal rather than disrupting the school day for thousands of our students across Toronto with a work stoppage," its chief operating officer, Terrie Lowe, said in a statement.

Bird says parents whose children might be impacted by a strike will be receiving letters from their schools. Should a strike take place, he said, families should make alternative arrangements for transporting their children to and from school, and to be sure to report any absences.

Further updates will be posted on the boards' Twitter accounts and websites.