TEACHERS and support staff at Huddersfield's biggest school are considering strike action.
The move comes in a long- running dispute with the school's governors and management.
Unions held a crisis meeting at Colne Valley High School, Linthwaite, on Monday - just as Government Ofsted inspectors were assessing the school.
Members of the NASUWT teaching union and Unison, which represents support staff, met to discuss their next move.
The meeting was not supported by members of the National Union of Teachers, which felt the timing was wrong.
It is believed staff are upset at many issues over the management of the school.
But governors say the current action centres on a row over a meeting.
Mavis Garnett, secretary of the Kirklees branch of NASUWT, confirmed the two unions were taking action.
"The NASUWT has declared an official collective dispute against the governing body. They had a meeting yesterday off the school premises," she said.
"The governing body will have to respond to the official dispute, which is about issues at the school.
"When we have got a response from the governing body we will be able to say that matters have been resolved or that they have not and we are going somewhere else."
Mr Mike Forster, of Unison, said: "There has been a huge problem with communication within the school. We are trying to sort it out amicably - but we are fast approaching a situation where that may not be possible.
"There is going to be a joint union meeting on the Tuesday after half- term, where we will have to discuss the governing body's failure to discuss our concerns.
"We are asking them to set up a joint consultative body, so we can consult with the school about all matters. But they are just stalling us," said Mr Forster.
Mr Howard Roberts, of the NUT, said: "We were not party to what happened in the current dispute. We are looking for a positive outcome for the benefit of the school.
"Our members did not want to have a meeting at this period for obvious reasons - but that does not mean they do not have concerns.
"They felt their concerns should be put on hold until after the Ofsted inspection," added Mr Roberts.
Colne Valley High School has 1,453 students aged from 11 to 16. The head teacher is Mrs Linda Wright.
Janet Jobber, chairman of the governors, said: "On February 3, the NASUWT asked the head teacher to provide a room at the school for a meeting of their members.
"The head teacher considered the request, but in her professional judgement felt the school could not accommodate a meeting on that date.
"The Ofsted inspection team would be working in the school and a parents' consultation evening would also be taking place. She offered two alternative dates, February 6 or the week after half-term.
"The governors and head teacher wholly support the right of union members to meet and are disappointed that the NASUWT felt unable to accept one of the alternative dates," added Ms Jobber.