Headteachers spend a quarter of their time on mundane administrative tasks such as going through their emails and post, arranging cover and planning school trips, according to the National College for School Leadership.
The college asked 34 serving headteachers to keep detailed journals for a fortnight. The study found that administrative tasks took up more of their time than any other activity. Only 15 per cent of the headteachers' days were spent on management itself and a mere seven per cent on strategic leadership. The figures echo a PricewaterhouseCoopers study into headship.
It found that heads were too involved in day-to-day chores, with some wasting valuable time on tasks such as unblocking toilets and filling dishwashers.
Penny Cox, headteacher of Holy Trinity CE primary in Richmond, Surrey, said she was not surprised. "When you factor in email, administration can easily take up a large portion of your time," she said. "It's very hard to fit in strategic leadership. Heads are encouraged to set aside time for that work and even do it off the premises to avoid being distracted."
The heads in the college's "Life in the day of a headteacher" study also complained of long hours. Their journals suggested an average working week of 52.9 hours, with women working slightly longer than men.
The research showed most heads had at least one late evening event to attend per week and worked at weekends. Around a third of those surveyed said their workload was demanding, stressful and draining.
Last year's School Teachers' Review Body report revealed even longer average hours - 53.5 for primary heads and more than 65 hours for secondary.
When the subjects of the college's study were asked what they would change about the job, more than 40 per cent cited the bureaucracy and external accountability, with league tables.
The research was carried out in preparation for a wider survey of 1,000 headteachers. Cary Cooper, professor of organisational psychology and health at Lancaster university, said the larger study would look at heads'
"coping strategies" and how they compared with other professions.
A National Association of Head Teachers study last September revealed that many heads were too tired even for sex.
Mick Brookes, general secretary of the association, said: "Primary heads spend a lot of time dealing with things such as emails and sorting out cover lessons. They don't have large teams so they have to do it themselves."