Children across much of Scotland are missing lessons as school support staff walk out after their union rejected a pay offer.
Unison has a mandate to strike across 24 council areas on Tuesday, Wednesday and Thursday.
Only eight regions in Scotland will be able to continue lessons as usual, and many council areas including South Lanarkshire, Fife, Inverclyde, Orkney and the Western Isles, will close schools.
The dispute is over a revised pay offer from umbrella body the Convention of Scottish Local Authorities (Cosla) for a pay increase for janitors, cleaners, and support workers, who are some of the lowest paid council employees.
GMB Scotland and Unite have suspended strikes while they consider it.
A new offer represents a minimum wage increase of £2,006 for those on the Scottish Government’s living wage and a minimum increase of £1,929 for workers who are earning above the living wage.
The living wage of £10.85 will rise to £11.89 under the new offer, equivalent to a 9.6% increase – but Unison has said the revised pay offer remains a “real terms pay cut” and “below the rate of inflation”.
But Unison rejected the offer as “an increase of only 0.5% in-year” for the majority of staff.
Some regions have come up with compromises to allow education to continue despite strikes.
Highland Council said 27 of its schools are expected to remain open while Glasgow City Council said high schools will be open for S4-S6 pupils only, on Tuesday, with a reassessment planned that day on whether any more schools and nurseries can open for the following two days.
First Minister Humza Yousaf urged for strikes to be reconsidered and said he believed it “is a very good offer indeed”.
Chair of Unison Scotland’s local government committee, Mark Ferguson, said: “The offer is still below the rate of inflation meaning that local government workers are being asked to take a real-terms pay cut during a cost-of-living crisis.”
Cosla said the “pay package not only compares well to other sectors but recognises the cost-of-living pressures on our workforce and which would mean the lowest paid would see an in-year uplift of over £2,000, or just under 10%”.
A spokesperson for Cosla said: “This is a very strong offer that equates to 10% or £2,006 for the lowest paid at the request of the trade unions.
“Throughout these negotiations we have met every request of our trade union colleagues.”
