Marking and lesson planning are the key drivers of workload stress among teachers, a study suggests.

For every additional hour that teachers spend on marking, there is a significant link with a decline in their wellbeing at work, according to the University College London (UCL) paper.

But other aspects of the job - such as time spent teaching and working with colleagues - seem to have “little direct effect upon teachers’ quality of working life”, the report suggests.

Read: Teachers quit because they find workload ‘worse than expected’

Workload: At least 70% of teachers working over contracted hours

Case study: Three hours’ sleep and surviving on Diet Coke

Researchers warned that adding an extra hour or two of work on teachers who already work 60 hours a week could be the “straw that breaks the camel’s back”.

Teacher stress: The impact of marking and lesson planning

The study, which analysed data from the 2018 Teaching and Learning International Study, also included survey answers from 9,405 teachers in five predominantly English-speaking education systems from England; Australia; Alberta, Canada; New Zealand and the United States.

Mary Bousted, joint general secretary of the NEU teaching union, said: “Teachers are still working amongst the longest hours in Europe, and this is clearly linked to heavy workload of lesson preparation and marking, resulting in poor wellbeing rates.”

She added: “It is not the core work which teachers find stressful but the piling on to the working day of a set of accountability requirements that exist solely to please government and Ofsted and offer little educational value. They do, however, drive high stress and poor wellbeing levels in teachers.

“High workload also leads to retention problems in the workforce, which this government has consistently failed to avert. The latest threat of a pay cap in this week’s spending review adds insult to injury.”

The report highlights other recent research by the UCL Institute of Education, which found that a quarter of teachers work more than 59 hours a week.

Lead author Professor John Jerrim, from the UCL Institute of Education, said: “Our study shows that it is not just a case of saying extra hours lead to extra stress among teachers, but what they are doing in those hours.

“We found that for every extra hour teachers spend on marking and planning, there is a significant association with decline in wellbeing at work. This is most likely because these are often tasks done in the evening, weekend and during school holidays.”

The study also found that the relationship between teachers’ working hours and their wellbeing may not be linear.

If teachers worked 35 hours a week, adding an extra hour may not lead to serious consequences.

“However, for those working 60 hours a week, an additional hour or two of work could be the straw that breaks the camel’s back,” Prof Jerrim said.

A reduction of five or 10 hours among those teachers who currently work 60 or more hours per week could potentially lead to an appreciable increase in this group’s quality of life, the report says.

Co-author Dr Sam Sims, also from UCL Institute of Education, said: “There are two clear areas where reducing teachers’ workloads would help reduce stress: lesson preparation and marking.

“With respect to the former, perhaps the easiest thing that policymakers can do is dramatically reduce examination, curriculum and inspection reforms - all of which create new work for teachers, who are forced to change lessons, materials and teaching styles as a result.”