New survey includes teachers among the hardest working professionals in the UK. They contribute an average of 48-hour week over a period of one year, considering into account the long holidays.
More than 80 percent fear that the "hidden hours" they spend -planning lessons are damaging their health, and 55 percent worry about the impact it would have on their personal life.
The poll undertaken by teaching website tesconnect.com found 55 percent of teachers regularly spend more than 56 hours a week grafting during term time.
With holidays, they average 48.3 hours, just below managers in mining and energy industries, who average 49.6 hours.
The poll found that 48 percent of teachers spend more time preparing lessons than they spend teaching, with 78 percent saying that they spent time on Sundays planning work.
"It comes as no surprise to us that teachers are among the hardest working profession," the Mirror quoted Tesconnect's Louise Rogers as saying.
"Every week teachers spend thousands of hours preparing their lessons for the classroom.
"Our site is busiest on Sunday afternoons. When most other professions are taking a rest, teachers are busy preparing for the week ahead," Rogers said.
Other professions weekly working hours, using official government figures, are:
Advertising and PR directors (42.2 hours)
Financial Institution managers and directors (40.9)
IT Engineers (39.0)
Chief Executive Officers (38.5)
Medical practitioners (38.4)
HR managers and directors (38.0)
Barristers and judges (36.0)