Teachers at Langdale Free School in Blackpool are planning to resume strike action on Tuesday and Wednesday.
The action is in protest against “unacceptable” terms and conditions of employment and “oppressive” management practices.
The National Education Union (NEU) states that qualified teaching staff at the school are paid substantially less than staff at other schools in the resort, and across the country, at a time when there is a recruitment and retention crisis in education.
As a free school Langdale, which has 130 pupils, sits outside local authority control.
Nadeem Siddiqui, senior regional officer for the NEU, said: “The teachers have been buoyed by the overwhelming support that parents and the local community have given them.
“Despite this, managers at the school continue to refuse to recognise the seriousness of the concerns or to engage in any talks with the Union, despite repeated attempts to persuade them to do so.
“Instead of seeking to find solutions which could avoid the continuing industrial action, leaders have instead focused on methods of intimidating staff.”
Free schools were set up as another model for education after the 2010 General Election. They allow individuals or groups, with business interests, to set up schools and to depart from normal school teachers’ pay and conditions, whilst taking away local democratic accountability.
Alison Forrest, Chair of Governors, said: "Langdale Free School are committed to ensuring the best possible conditions of employment for its staff and will continue to attempt negotiation with staff to that end.
"LFS will make every effort to minimise any disruption that may be caused as a result of the action and apologises for any inconvenience the National Education Union action may cause.
"There will be no further public comment from LFS on this matter."