Excessive workload is having a detrimental effect on the home life of 85 per cent of independent school teachers, an Association of Teachers and Lecturers' survey has found.
ATL spoke to 300 of its members in the independent-school sector which is not covered by the deal designed to cut teacher workload in state schools.
The union, the biggest in the sector representing a quarter of its teachers, found that 60 per cent of those surveyed worked more than 50 hours a week.
Excessive workload left 35 per cent feeling exhausted and stressed on a daily basis, while 30 per cent said they had no time for a social life.
Almost two-thirds (64 per cent) said they were expected to perform tasks teachers should not have to do. These included photo-copying, break-time supervision and washing and ironing PE kits.
A 38-year-old female teacher at a girls' boarding school in southern England said: "My eight-year-old daughter hates my job. She especially detests it when I have to teach on a Saturday morning and have my Monday night boarding duty. This leaves me with a lack of quality time to spend with her."
Delegates at the union's conference in Bournemouth passed a resolution calling for improved conditions in the sector including action by schools to address workload, and a right to one-and-a-half days of undirected time during every seven-day period of term-time.
The Independent Schools Council said the survey was too small to draw any conclusions.