Teachers across England are staging a 24-hour strike in a long-running dispute with the government over the "underfunding" of schools.
Rallies and marches will take place on Tuesday after members of the National Union of Teachers voted by more than 9-1 in favour of industrial action.
The union has written to Education Secretary Nicky Morgan calling for "meaningful" discussions to tackle issues it said were negatively affecting education.
Specifically, it wants to:
increase funding to schools and education
guarantee terms and conditions in all types of schools
resume negotiations on teacher contracts to allow workload to be addressed
Acting general secretary Kevin Courtney apologised for the "disruptive" strike action but said the challenges facing education were "too great to be ignored".
He said the "worst cuts in school funding since the 1970s" are damaging young people's education.
"No parent wants this for their children. No teacher wants this for their school or pupils."
Addressing the issue of funding, Education Secretary Nicky Morgan said: "To suggest we aren't prioritising school funding is disingenuous.
"The significance we place on education is demonstrated by the fact that we are investing more than any previous government in our schools.
"This year the schools budget will total around £40bn, an increase of around £4 billion since 2011-12, so it is now the highest it has ever been."