Many teachers working in independent schools regularly work more than 50 hours a week, a survey suggests.
Expectations of teachers in the independent sector are high
A poll of over 1,000 public school teachers found 85% had seen no improvement in their work-life balance in the course of the past two years.
And nearly half - 47% - felt stressed as a result of their workload.
The Association of Teachers and Lecturers, which conducted the survey, said schools must work to implement better work-life balance policies.
"I feel that keeping classes open at weekends and until 9pm every night during Lent term is expected, not extra," one teacher told the ATL.
"I seem to say to myself just get through this week and then it should ease up... but it doesn't," said another.
Independent school teachers are not covered by the workload agreement, where teachers have a guaranteed 10% of their timetable allocated for preparation, planning and assessment (PPA) time.
But Dr Steven King from the Independent Schools Council said: "There is indeed an expectation that teachers in the independent sector contribute fully to school life and that can mean longer hours and a longer working day.
"The associated benefits, though, are enormous: longer holidays, better facilities, increased scope for specialization, often more pay, smaller class sizes and a more disciplined classroom regime," said Dr King.
"It is no wonder then that last year three times as many teachers moved from the state sector to the independent sector as moved in the other direction."
In a further survey, the ATL found support staff in state schools were not getting the pay and recognition they deserved.
The union claims one in three support staff have not had a pay rise to reflect new supervisory roles.
Since the introduction of PPA time for teachers in September 2005, some support staff can supervise classes.
But the ATL says many are asked to do more than supervise teacher-set work.
In a survey of 528 support staff members in England and Wales, the union found 66% of cover supervisors were being asked to do more than just supervise classes.
"This goes against national guidance from the workforce agreement monitoring group, which says those working in cover supervisor roles should not be required to do more than supervise work set by a teacher during a short-term teacher absence," the ATL says.
The union, which is meeting for its annual conference in Gateshead, says only 67% of staff have had a pay rise to reflect their new supervisory roles.
Dr Mary Bousted, general secretary of ATL, said: "Schools need to do more to recognise the value of their support staff.
"Support staff are playing an increasingly important role in schools, and this has to be reflected in the way they are treated," she said.
"Schools should not have any excuse for not paying support staff for the work they are doing and their contribution to school.
"We will be taking this issue up with the DfES, and will fight to support any members who are having problems getting their pay, status and role enhanced in line with the national agreements accepted by the unions and employers."
Schools Minister Jacqui Smith told ATL delegates: "Support staff are making a difference in the classroom, in the playground, in the dining hall and the office.
"Of course that contribution should be properly rewarded and we want to make sure support staff get a fair deal.
"That's why we have set up a working group with support staff unions and employers which will review a whole range of employment issues."
The group would report back at the end of the month, she added.