A protest has been held outside a Northampton school over the working hours of a union official.
Duston School teacher Pat Markey, group secretary of Northamptonshire's branch of the National Union of Teachers (NUT), had been given a day a week for union business.
That has now been revoked by the school which means that Mr Markey has no time for union affairs.
The school says it is not bound by any laws to give time off to lay officials.
John Buckle from the NUT, which organised the protest, said: "Historically the local authority has allowed lay officers like Pat time off for union duties."
'Strains on school'
The school's governing board has been reviewing all contracts as it moves into academy status.
The head of Duston School, Jane Herriman, said: "To release someone for that role might actually put strains on the school here and affect the quality of teaching."
There are more 1,000 members of the NUT in the county.
"Pat has a heavy case load to deal with concerning issues like pensions and pay," said Mr Buckle.
Duston School has been looking at improving the quality of teaching it offers.
"It makes it quite constricting to look at the progression and continuity of teaching and learning when somebody might not be in on a regular basis," said Mrs Herriman.