Almost all teachers are still working more than 50 hours a week despite massive investment designed to cut workload, new research reveals.
Only secondary heads of department and special school teachers have an average day of fewer than 10 hours, the annual survey of teachers' workload shows.
There has been no significant reduction in the working hours of classroom teachers since 2000, the Government-sponsored survey found.
The persistent long-hours culture has continued despite major reforms designed to reduce the administrative burdens on teachers.
Changes introduced since 2003 include the delegation of clerical tasks to support staff, limits on covering for absent teachers and guaranteed time for planning, preparation and assessment.
But secondary classroom teachers are working an average of 50.4 hours a week this year compared to 51.3 in 2000. Primary teachers are working 51.2 hours a week, only slightly down from 52.8 in 2000.
Hours worked by secondary school heads have been volatile, but they continue to have the longest working weeks, currently averaging 58.6 hours, down from 65 hours three years ago.
The working hours of primary school heads have fallen since 2000, but have risen consistently since 2005, the survey shows.
The findings follow other Government-commissioned research, published last month, which found any reductions in hours achieved by workforce remodelling had been wiped out by new initiatives.
Teachers did suggest, however, that changes made to the school workforce had cut stress levels and made it more possible for them to focus on teaching.
John Bangs, head of education at the NUT, said that the failure to cut long working hours was not a surprise.
"Until the high-stakes nature of league tables is removed and teachers are trusted then working hours are very unlikely to reduce," he said.
"Excessive planning and reporting to parents is a waste of time. These have filled the vacuum created by cutting administrative tasks."
Mick Brookes, general secretary of the National Association of Head Teachers, said: "There has been downward pressure on bureaucracy for classroom teachers, but the same has not been true for heads, especially in smaller primary schools.
"They have to do all the administrative work and also a considerable teaching timetable. The vetting, barring and compliance legislation is a real headache and stops people going for headship."
The survey analysed the working patterns of 1,572 randomly selected teachers in primary, secondary and special schools in England and Wales.