More than 40,000 members of the B.C. Teachers' Federation were being asked to support a strong mandate for a full strike as a pressure tactic to get a new collective agreement.
The unions representing 34,000 education support staff came to a tentative deal with the province over the weekend after just five days of bargaining.
Education Minister Peter Fassbender said it was another example of a union taking what the government is willing to offer.
"My hope is that this could send a signal to the BCTF," Fassbender told reporters. "This financial agreement is in line with the other public sector unions."
The earliest date that all schools could be shut down is June 16 after the employer gets the required three days' notice of a full walkout.
The vote comes at a time when the union's strike pay account is so depleted it can't pay each teacher $50 a day to walk the picket line and the B.C. government is asking the provincial labour board to declare tests for senior grades to be made essential.
Local union chapters were organizing the ballot, with the union planning to announce results Tuesday night.
"The higher the turnout and the higher the Yes vote, the more pressure it puts on the government to bring resources to the table," said a BCTF memo available online to members last week.
The memo said the economic benefits of a "good settlement" will have a positive long-term effect for members, in spite of salary losses due to job action. Even a one per cent increase for a new teacher will amount to a $15,000 salary boost over a 30-year career, it said.
Teachers have been without a contract since June 2013. Wages and classroom conditions are the major issues.
For every day teachers are on the picket line, the government saves $12 million and another $4.5 million for support staff, according to the Education Ministry.
The union wants a wage hike in the range of 12 per cent over four years, while the government contends that spikes to more than 19 per cent when compounded, and including benefits.
The employer has offered 7.3 per cent over six years plus a $1,200 signing bonus if a deal is reached by the end of the school year.
Vancouver teacher Aeryn Williams said she supports her union.
"I feel like we should be playing hardball because the government isn't putting students first," said the Grades 2 and 3 teacher.
But as teachers consider a full walkout, their co-workers under CUPE and other unions agreed to a 5.5 per cent wage increase over the five-year contract.
The agreement reached on Saturday by the Canadian union of Public Employees and eight other unions representing support staff still needs to be ratified and covers workers including school secretaries, caretakers and bus drivers.
The fact that CUPE has reached a deal as the BCTF remains deadlocked hasn't changed the unions' commitment to support teachers, said B.C. chapter president Mark Hancock.
"Just as the teachers have been at our side as our members have fought for public education, we continue to stand with them," he said in a statement.
Fassbender said there's a difference between the two unions' negotiation strategy: "A willingness to sit in the room and bargain realistically on all the elements."
Support staff will not be punished for refusing to cross BCTF picket lines and they will be compensated for lost wages, the minister said.
Teachers started limited job action on April 23, pulling back some limited duties.
On May 26, a second stage meant rotating strikes closed each school one day per week. A third week of similar strikes begins Tuesday, with districts shutting down schools until Friday.
The employer locked out teachers in conjunction with the rotating strikes and the B.C. Labour Relations Board subsequently ruled it was within its rights to chop teachers' pay by 10 per cent.
The employer has also asked the tribunal to designate the marking of exams for Grades 10 to 12 as essential, although a hearing hasn't yet been set.
Negotiators are scheduled to continue bargaining through to Thursday.
Follow @TamsynBurgmann on Twitter