Pupils at nearly every primary and secondary school and many council nurseries are affected by the industrial action over pay.
Schoolchildren stayed at home as teachers across Scotland walked out in their first national pay strike since the 1980s.
Every school on the Scottish mainland will be shut as thousands of teachers in the Educational Institute of Scotland (EIS) walked out over pay, with a last minute revised pay offer on Tuesday being branded as "insulting" by unions.
Education Secretary Shirley-Anne Somerville warned the Scottish Government’s budget is under “extreme pressure” and the 10 per cent rise demanded is “unaffordable” after a last-ditch offer was made in a bid to avert the strike.
The EIS now represents about 80 per cent of the country's teachers and its actions are closing almost all primary, secondary and additional support needs schools.
Only a handful of primary schools in Orkney and Shetland will remain open.
The Scottish schools strike are part of action being held across the country.
Picket lines were mounted outside schools, universities and Royal Mail centres on Thursday as tens of thousands of workers went on strike in worsening disputes over pay, jobs and conditions.
The general secretary of the Communication Workers Union (CWU) accused Royal Mail of subjecting its workers to a “psychological attack”.
Speaking at a picket in Camden, north London, Dave Ward told the PA news wire: “What they’re doing is threatening our people every day. If they leave behind mail because they can’t complete it in their normal work time, they’re being threatened with the sack.
“They’re been pushed around to this delivery, that delivery, they’re being refused overtime when there’s mail in the office. They won’t pay out overtime for our people.
“They’d rather have the quality of service failures and then they blame it on the postal workers.
“And genuinely, we’ve seen people resigning from the job because they’re sick and tired of the attacks that are going on in work.
“It’s a psychological attack.”
The union has rejected the company’s “final” offer and is pressing ahead with a series of strikes in the coming weeks, including on tomorrow’s Black Friday and on Christmas Eve.
Around 70,000 members of the University and College Union (UCU) will strike on Thursday and Friday, and again on November 30, in a dispute over pay, pensions and contracts.
It will be the biggest strike of its kind, affecting an estimated 2.5 million students, with the union warning of escalated action in the new year if the row is not resolved.
The union says lecturers and other academic staff have suffered a decade of below-inflation pay rises, with a 3 per cent increase announced in the summer.
UCU general secretary Jo Grady joined a picket line in Manchester, telling PA that UCU members have “had enough” of falling pay, pension cuts and gig economy working conditions.
“Our members are absolutely up for this strike in huge numbers because they know what is at stake.
“Universities have £40 billion in reserves but appear to be more bothered about buildings than people.
“Around 90,000 staff are on fixed terms contracts. They want a career but are being prevented from putting down roots.”