Image caption The summer holidays could operate to a different timetable in different schools

Allowing all state schools in England to set their own term times could cause "chaos" for families booking holidays, a teachers' union is warning.

Plans were announced on Monday to allow all schools to vary term dates, a right already held by academies.

But the National Union of Teachers says it will cause problems for families with children in different schools.

Term times should be decided by heads and not councils, says the Department for Education.

"It is right that all schools are free to set their own term dates in the interests of parents and pupils," said an education department spokesman.

In Wales, there is a shift in the opposite direction, with plans to give the government powers to set the same holiday times for all state schools in the country, to avoid differences for families with children in different authorities.

There is currently no legal duty on councils or governing bodies in Wales to work together on holiday times.

Holiday savings

From September 2015, all state schools in England will be able to decide their own term dates, under plans for more school autonomy announced by the government.

The changes have meant we're able to have equalised blocks of working which is much better for curriculum planning and it's much better in terms of levels of student and staff exhaustion Ros McMullen, Principal, David Young Community Academy

It could mean that more state schools switch from the long, six-week summer holidays.

Christine Blower, head of the NUT, said it would not mean saving money for families.

"Holiday companies will almost certainly just expand the period over which they charge premium rates so there will be no benefit to families, or indeed the general public who will have fewer weeks of less expensive holidays," she said.

Head teachers warned that parents with children in different schools would still expect local schools to agree common dates so that families could plan holidays together.

Schools can already vary the shape of the school day, but they will also be able to change the length of their terms.

Labour's education spokesman Stephen Twigg announced last month that a future Labour government would extend these academy flexibilities to all state schools.

It means that both the coalition government and opposition are pushing for greater powers to be devolved to individual schools.

Local co-ordination

The plans put forward in the Deregulation Bill would mean schools that are not academies would not have to accept the term dates set by local authorities.

A majority of secondary schools are now academies, but most primary schools have not adopted academy status - so this would represent an extra level of flexibility for them.

They would still have to operate within a legal limit of a minimum of 190 school days each year.

The problem will come if no one is responsible for creating a co-ordinated calendar for an area and it turns into a free-for-all Brian Lightman, Association of School and College Leaders

Among the schools that have experimented with term lengths is the David Young Community Academy in Leeds, which has a year of seven shorter terms and holidays that are not longer than four weeks.

Principal Ros McMullen said that cutting the summer break and extending other holidays was "very popular because of course there are cheaper holidays for families".

She also said there were academic gains. "The changes have meant we're able to have equalised blocks of working which is much better for curriculum planning and it's much better in terms of levels of student and staff exhaustion."

The Boulevard Academy in Hull is going to cut the summer holiday from six weeks to four weeks.

"It is right that all schools are free to set their own term dates in the interests of parents and pupils," said a spokesman for the Department for Education.

Head teachers' leader Brian Lightman said: "Most schools choose to follow the local authority calendar because they know that it's better for parents who have children in different schools and teachers who want their holidays to coincide with their children's.

"The problem will come if no one is responsible for creating a co-ordinated calendar for an area and it turns into a free-for-all.

"Somebody needs to take the lead locally on deciding term dates and it makes sense for this to be the local authority, even if schools aren't required by law to follow it," said Mr Lightman, general secretary of the Association of School and College Leaders.