Several thousand University of Toronto teaching assistants went on strike Friday evening, surprising students hours after they received an email from the school suggesting a strike wouldn’t happen.

A tentative agreement had been reached with the university administration around 3 a.m. on Friday, but members crowded into Convocation Hall on Friday night and – in a rare move – voted to reject the deal.

Erin Black, chair of CUPE 3902, sent out a statement Friday evening that said picket lines will go up Monday.

“We are poor, precarious and we need an increase in our standard of living,” Black said.

“We deeply regret the inconvenience this will cause students,” Black added.

The strike may impact tens of thousands of students as they enter the final weeks of the semester at all three campuses of Canada’s largest school.

Although the university administration says most classes are expected to continue, “there may be some classes, labs or tutorials that may need to be cancelled due to strike-related absences.”

The administration says students should expect it to take longer than normal to get to classes during the strike.

Transit on campus may be affected if bus drivers choose not to drive through picket lines, according to the school.

The administration says students remain responsible for fulfilling course requirements, even if they choose not to cross picket lines in solidarity with those on strike.

Professors are also expected to continue to teach.

In a letter sent earlier this week, University of Toronto Faculty Association president Scott Prudham advised professors to “do no less but also no more than regular duties in the event of a strike.”

“It is important for those who may wish to honour labour solidarity to understand that, as faculty and librarians, we are not in a position to withdraw our own labour in the context of a CUPE work stoppage,” he added.

Although Prudham’s letter said he hoped U of T would allow classes to be held off campus at professors’ discretion, the administration warned students on Friday that courses held off campus are “not officially sanctioned.”

Meanwhile, teaching assistants at York University could also be on the picket lines as early as Tuesday.

At issue on both campuses is the approximately $15,000 annual funding package that graduate students and post-doctoral fellows receive in exchange for the work they do while studying.

CUPE says that teaching assistants provide about 60 per cent of the undergrad instruction at both schools.