Around 1,000 headteachers are set to attend a mass rally outside Parliament to demand more money for schools.

The heads, from the Worth Less? campaign, want the government to ensure that its long-awaited teacher pay announcement is fully funded.

They are also calling for emergency funding for sixth forms, and to support pupils with special educational needs and disabilities (SEND), including those with “high needs”.

In addition, they want to see improvements to teacher supply and retention, and “enhanced social mobility for the most vulnerable and disadvantaged students and pupils that we serve”.

On 28 September, the campaigners plan to gather at Parliament Square before delivering a petition to Downing Street.

Headteacher Jules White, who founded Worth Less?, said the event was “completely unprecedented” owing to its scale and the involvement of heads from the furthest corners of England.

He added that they were not campaigning for higher teacher pay but for enough money to pay for a fair settlement.

Mr White said the group’s message to government was: “You will cripple us if you direct us to make [pay] increases without more funding.”

He continued: “To run a really good school you need the fundamentals of a strong supply of great teachers and support staff and enough money to fund wraparound care for students. 

“Hundreds of millions has been wasted on structures, governance arrangements and pet projects which provide little more than a positively spun sound bite to the general public.”

A Department for Education spokesperson said: “The Education Secretary has been clear that there can be no great schools without great teachers.

“That is why we have committed to making sure that teaching remains an attractive and fulfilling profession, and are working with the unions to strip away workload that doesn’t add value, improve conditions and offer all teachers high-quality professional development.

“We are considering the STRB report carefully and will respond in due course.”