Ministers have been warned that school strikes could happen in the autumn if an improved pay offer is not made.
Larry Flanagan, general secretary of Scotland 's largest teaching union, the Educational Institute of Scotland (EIS), said teachers are ready to 'fight back'.
Teachers rejected a 2.2 per cent increase from the Convention of Scottish Local Authorities (Cosla) as the union demands a 10 per cent pay rise.
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During his speech at the union's AGM in Dundee on Friday, Mr Flanagan said teaching staff are taking the hit for the economic crisis.
Sounding the alarm for strike action, he said teachers 'delivered during Covid and frankly, in a post-Covid environment, we deserve better than what is being offered'.
He added: "Cosla and the Scottish Government are on notice that come the autumn we will be strike-ready if required."
It followed a similar message from union president Heather Hughes, who warned that school teachers are ready to "vacate classrooms" to demand change.
Mr Flanagan, in his address, also emphasised the need to prevent the attainment gap, rather than close it.
A 'singular failure' of the Scottish Government, he said, relates to the education of under-fives.
Nursery teachers in pre-fives are being "marginalised" despite research showing the 'efficacy' of their role.
He said: "It seems to me that it makes more sense to prevent the attainment gap establishing itself than to engage in a Sisyphus-like struggle to close it - and securing the role of nursery teachers is the most fundamental step to achieving that."
The union has previously called on the Scottish Government to address the decline in the number of nursery teachers, after 2020 EIS research revealed a 39% decrease over a 10-year period.
The research found that nationally, 25.7 per cent of nursery children aged three to five did not have access to a teacher - with only 12 of 32 local authorities continuing to employ full-time early years teachers.
Early years teachers, he said, have the ability to nurture children's potential in order to prevent significant disadvantages following children through primary and secondary education.
And he called on politicians 'to stop their constant bickering' and ensure teachers are properly resourced to support pupils.
Education Secretary Shirley-Anne Somerville is also expected to address union members at Dundee's Caird Hall.
