Thousands of teachers from across Scotland have held a march and rally in Glasgow in support of a pay demand.
Members of the Educational Institute of Scotland (EIS) want a 10% rise after years of pay restraint.
The EIS said the value of teachers' pay had fallen by more than a fifth over the past decade.
Employers have tabled a "final" offer of 3% for all but the most highly-paid teachers, with some grades receiving bigger rises.
Education Secretary John Swinney has described the offer as generous and fair, but the union has dismissed it as "divisive".
Teachers assembled in Kelvingrove Park on Saturday morning, before heading off in a huge procession towards George Square.
The union said that up 30,000 people took part- a far higher number than expected.
It took two hours for all the demonstrators to clear the park and join the march.
Addressing the Rally in George Square, EIS president Alison Thornton said, "Nine years of pay settlements under the public sector pay cap have resulted in the value of our take home pay being down by nearly 25%.
"The salaries of teachers in schools in Scotland are below the European average and those of other countries in the wider world. Our pupil contact hours are high, and we still work an average of 11 hours of unpaid overtime each week to deal with the demands of the job.
"No wonder teacher recruitment and retention is in a crisis situation. Austerity doesn't work, quality public services need proper funding and by investing in teachers then there is investment in education and our young people and their futures."
EIS general secretary Larry Flanagan said: "Look at the magnificent array of EIS and school banners from across the country, and the banners, also, of other public sector trade unions whose members, like teachers, have been under the cosh of austerity for the past decade.
"Those who want to split the unions - think again, public sector trade union solidarity is a given. Our pay claim is for 10% - given that the value of take-home pay has dropped by 24% in the last decade, that claim is already a compromise on what we deserve."
The education secretary insisted he valued teachers, and that the Scottish government was contributing an extra £35m for teachers' pay.
In a statement, Mr Swinney said: "Through a combination of a 3% increase for all staff earning up to £80,000, restructuring the main grade scale and annual progression, the majority of teachers receive a rise between 5% and 11%.
"There would be a flat rate increase of £1,600 for those earning more than £80,000 from 1 April 2018."
But the union has recommended its members reject it in a ballot which opens next week.
The EIS general secretary said "smoke and mirrors" were being used to pit unpromoted teachers against their promoted colleagues.
Mr Flanagan added: "The conflation of incremental progression, which teachers would always have received anyway, with this pay offer to make it appear more attractive is a shameful tactic drawn straight from the book of bad management."
Teachers' pay is negotiated by a committee which includes the unions, councils and the Scottish government.
Councils employ teachers but pay and conditions are set nationally and councils receive much of their funding from the government.
A spokesman for local government body Cosla said: "Following a vote, council leaders took the decision to jointly, with the Scottish government, write to teachers spelling out the value and merits of the pay offer currently on the table.
"This joint letter will be written with input and advice from the appropriate professional associations within councils."
As well as EIS leaders, the speakers at the rally included STUC president Lynn Henderson, NUS president Liam McCabe, Scottish Labour leader Richard Leonard, Scottish Greens MSP Ross Greer, SNP MP Chris Stephens and Carole Ford for the Scottish Lib Dems.