Renfrewshire's largest union has launched an industrial action ballot of almost 1,000 schools.
The ballot is over a pay dispute for all council workers and voting will close on Friday, August 25.
If staff vote to strike, there could be mass school closures across Renfrewshire in September.
School staff are being asked to vote in the dispute and the union will decide on whether to ballot additional groups of workers in the coming months.
Mark Ferguson, chair of Unison's Scottish Local Government Committee and Renfrewshire branch secretary, said: "Cosla's offer falls short of Unison's pay claim, it also less than the offer made to the lowest paid local government staff south of the border.
"And it would be a real-terms pay cut during the cost of living crisis.
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"Despite efforts to move negotiations along, we're now at an impasse. Cosla has refused to improve its pay offer, which Unison members overwhelmingly rejected.
"It also says it doesn't have the cash to offer more but is also refusing to ask the Scottish Government for additional funding.
"Council and school staff are fed up. All school staff should look out for their ballots, which will arrive in purple envelopes, vote and post back as soon as possible."
A Cosla spokesman said the "strong offer" raises the local government living wage by 99p to £11.84 per hour.
He said: "The reality of the situation is that as employers, council leaders have made a strong offer to the workforce. A strong offer which clearly illustrates the value councils place on their workforce, and it compares well to other sectors.
"It recognises the cost-of-living pressures on our workforce and, critically, it seeks to protect jobs and services."
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