Teachers and lecturers work more unpaid overtime than any other occupation, according to a league table of working hours.
The table, compiled by the TUC, reveals how the £23bn of unpaid overtime worked in the UK last year breaks down between different occupational groups.
It shows that teachers and lecturers work an average of 11 hours 36 minutes in unpaid overtime each week - almost two hours more than corporate and senior managers.
But because they are paid so much more, senior managers' overtime is worth much more than any other groups.
Weekly unpaid overtime of nine hours and 48 minutes for senior managers on average pay is worth £19,000 a year, but teachers' longer hours are worth only £9,892.
Finance and accounts staff are the biggest group of white-collar staff who rank high in the unpaid overtime league table.
Those who do unpaid overtime put in seven hours 18 minutes a week on average, worth £6,000 a year.
The TUC published the league table to mark national Work Your Proper Hours Day, which takes place on Friday (25 February).
During the day, the TUC is advising staff to work only their contracted hours and encouraging managers to thank employees for their extra work, by, for example, buying them a post-work tipple.
On average, people's unpaid overtime is worth £4,650 a year, although evidence suggests that many of the extra hours worked are voluntary.