Teachers would be guaranteed a six-week summer holiday if they agree to take part in training in their own time, campaigners for a six-term year said this week.
They want all local authorities to force schools to scrap the five floating in-service training days, in favour of training after school, at weekends and even during holidays.
Chris Price, a key adviser on the six-term year, said up to 60 per cent of LEAs were already using similar arrangements.
But the remainder, and some teaching unions, still needed persuading.
He said: "We don't care if they do it while lying on the sand in Corfu. As long as they are doing work which is approved training, and which will make them better teachers, I don't see any reason why this should have any relation to the school year."
Teachers are required to be available for work for 195 days a year, although pupils are only in school for 190 days.
Schools have to decide when to take their five training days and this can differ from one school to the next, affecting budgets and attendance.
The Local Government Association, which is spearheading the changes, claims that when education chiefs organise school transport, they have to plan for 195 days regardless of whether all pupils in the authority are in school.
If teachers' school year was also reduced to 190 days LEAs would save millions of pounds in transport costs and remove the need to hire buses for days when some pupils are at home.
It would also enable the police and truancy officers to weed out pupils who are using teacher training days as an excuse to skip off lessons.
Mr Price said the proposals would effectively give teachers an additional week off which could be added to the summer holiday, guaranteeing staff six weeks off when the new term structure comes into force in some local authorities in 2005.
The National Association of Schoolmasters Union of Women Teachers, in particular, had been opposed to any reduction in the six-week summer break.
It is also resisting any moves to force teachers to train in their own time.
Chris Keates, deputy general secretary, said: "If these changes go ahead there will be nothing to stop a headteacher from demanding that teachers come in in the middle of their summer holiday because there is a project he wants them to work on.
"We cannot see any reason why inset days are not calendared into the school year, with the start and end of each term being fixed and schools deciding which of the days in between they use for training.
"What is being proposed might look like a practical option but we anticipate problems."