Pushy parents are getting teachers sacked because private schools fear losing valuable business, a union warned yesterday.
Headteachers are "very sensitive" to complaints from parents who often pay fees of £20,000 per year, according to John Richardson, from the Association of Teachers and Lecturers.
Mr Richardson, ATL's national officer for independent schools, warned that many teachers in the private sector were not given basic employment rights.
"An employer will see the competition and will have their own agenda in terms of keeping up with the next school," he said.
"There is a certain amount of pressure which comes from parents who have very high expectations for exam results given that they have paid."
If a parent paying annual fees of £20,000 decides to withdraw their child because they are unhappy with a teacher, schools make "business" decisions to cut their losses, he claimed.
Some elite schools can afford to throw money at problems, sack teachers and pay them off. In one case, a teacher was called into the head's office because parents had complained that their child had only scored 90 per cent in an exam when they were expecting 95 per cent.
The union has 20,000 members in private schools - about a third of all teachers in the sector - and estimates that about 15 per cent do not have written contracts.
"There are a lot of teachers in the independent sector who are timid about exercising their rights for fear of upsetting their employers," said Mr Richardson.
With many staff living on site, they can lose their homes as well as their livelihoods if they are sacked, he added.
The union is calling on ministers to introduce a new test of "fitness" to run a school to stop unscrupulous employers taking over private schools for their own business purposes.
Tony Little, headmaster of Eton College, Windsor, said last year it introduced a 24-hour period off each week for the school's house-masters to help give them a better work-life balance during term-time.
"They have benefited from it hugely because it has given them a break.
"We are concerned to make sure that the workload is evenly shared, so that people can give their best," he said.