GCSE pupils in Bolton could soon be able to email their teachers for help out of school hours, if a government scheme gets the go-ahead.

The e-mentoring scheme will to be piloted next year as an alternative to traditional study leave, but teachers' unions and Bolton headteachers are not convinced it will work.

It follows a call by school standards minister David Miliband for schools to end the practice of allowing all Year 11 students summer study leave before their GCSE exams.

He based his argument on an experiment in 25 schools that showed students' exam performance leapt by nine percentage points when study leave was replaced by alternative revision strategies.

He said: "While some pupils may benefit from independent home study away from school, many more would benefit from a structured programme of study and revision at school, before and during the exam period.

"Study leave must not become videogame leave."

One of the alternatives to be trialled is to encourage GCSE candidates to email teachers with revision queries.

But teachers' unions have said the idea is unreasonable.

Malcolm Fullerton, Bolton representative for NASUWT, said: "I would think this flies in the face of the work/life balance that we are trying to achieve. It is potentially extending the hours of teachers and could impinge on their privacy.

"Many teachers are ex-directory because they don't want to run the risk of being harassed with abusive phone calls.

"This would leave them open to the same sort of thing happening by email.

"The idea needs to be treated with extreme caution."

Frank Vigon, headteacher at Turton school and chair of the Secondary Heads Association, said: "I don't have an argument with staff wishing to have pupils contact them by email. Some A-level staff at our school do it to a certain extent already.

"But I think that's a matter for individual teachers to decide, not for the government to decide for them.

"I find it helpful to have my students email so I can contact them about things, but I choose to do that and I have strong reservations about saying to teachers as a whole that they must provide their email address for pupils.

"If the government wants to provide something like they have with the NHS Direct service, where extra education staff are available out of hours for pupils to contact, then that should be separate to school teaching staff.

"I can see that something like this might be a development of the future, but it would have to be a separate entity to everyday teaching."

Margaret Blenkinsop, director for education and culture in Bolton, said: "This is something that would have to be managed.

"Systems are in place for students to get support, and it is important they link in with those services and make the most of them.

"I would be surprised if teachers in Bolton chose not to support their students, but at the same time, pupils must be mindful of the teachers' workload."

In answer to these concerns, a spokesman for the Department for Education Services said: "The pilot scheme will be limited to around 15 schools and designed so that it does not add to teacher workloads or expose them to potential email abuses.

"The trials would be entirely voluntary, with individual teachers volunteering to participate, and schools using the freedoms of workforce reform to manage the trial, perhaps also looking at time off in lieu or additional pay for volunteers.

"Students would need to enrol to participate in the scheme, and email would be subject to stringent security arrangements to prevent potential abuses."