Teachers and lecturers are working on average an extra 11 hours unpaid every week, figures from the government's Labour Force Survey suggest.
Teachers have often complained about long hours
The hours amount to teachers working for free from the New Year until 22 March, the TUC estimates.
If they were paid an hourly rate for the overtime, they would earn another £9,937 a year on average, the TUC said.
The government said teachers now had 10% of their working week for planning, preparing and assessing pupils' work.
The planning, preparation and assessment deal, which came into force in September 2005, follows earlier agreements to release teachers from administrative tasks and limit cover teaching.
TUC general secretary Brendan Barber said: "No-one says we should turn into a nation of clock watchers, or never put in extra time when there's a sudden crisis or sudden rush.
"But full-time staff in the UK work the longest hours in Europe, and are the most likely to do unpaid overtime."
The TUC has designated Friday 24 February "Work Your Proper Hours Day" and is urging workers to take a full lunch break and go home on time.
Time to plan
A spokesperson for the Department for Education and Skills said: "Our workforce reform measures are turning the tide on teacher workload and ensuring that teachers can focus on their primary task - teaching.
"And this year, teachers have been guaranteed 10% of their time free to plan, prepare and assess their lessons."
Chris Keates, general secretary of the NASUWT teachers' union, said: "The TUC is right to highlight that there is a continuing long hours culture in workplaces across the UK.
"The situation demonstrates graphically why the NASUWT worked to secure agreement with the government on changes to teachers' contracts which would bring downward pressure on excessive working hours."
She said there was evidence that the workload deal had helped cut teachers' hours.
Sally Hunt, general secretary of the Association of University Teachers, said the figures were not a surprise.
"Lecturers' workloads have increased massively over the years, despite their pay decreasing in relative terms."
The lecturers' union Natfhe agreed.
"Staff in further education colleges are putting in these extra hours even though 59% of colleges have not been paid pay increases that were due in 2004," said Natfhe general secretary Paul Mackney.
The unions have called a joint strike for 7 March over pay for academic staff.