Teacher Megan Quinn says she works a minimum of 56 hours per week - not to mention a few more on marking and lesson preparation.
She is just one of many thousands of teachers in England said to be burning the professional candle at both ends.
According to the Education Policy Institute, most full-time teachers work an average of 48.2 hours per week.
But one in five works 60 hours or more - 12 hours above the limit set by the European working time directive.
A teacher for eight years, Megan feels well supported by her school in north London and considers herself one of the lucky ones. She says she would love to commit to the job for the rest of her working life, but is not sure it is sustainable.
"Between the hours of 09:00 and 15:30 I am in my absolute element," she says.
But she says coping with government changes in assessment and accountability, and, as she sees it, with national tests set at too high a level for some of her children, she sometimes doubts whether she can continue in the job she loves.
"It's unmanageable for lots of new teachers coming into the profession in terms of what's expected of them.
"There are so many people coming into the job who are committed and really want to make a difference but it can be demoralising and often teachers are exhausted," she says.
The report, based on data collected in the OECD's Teaching and Learning International Survey between 2012 and 2014 - which compares the practices of teachers in secondary schools in 36 jurisdictions - finds teachers in England work longer hours than their counterparts in all but two of these states.
This extra time, however, does not equate to increased teaching time, rather it is spent marking work and carrying out administrative tasks.
Conversely, the survey found England's teachers near the bottom of the international table for continuing professional development.
Workload was found to be a significant barrier to accessing this up-to-date training on the latest teaching methods and material.
The report found despite working longer hours early on in their careers, new teachers could expect to earn a wage 16% lower than the OECD average.
EPI said its findings raised concerns not only for professional development and teaching quality, but also for the wellbeing of teachers themselves.
It adds: "With pupil numbers in secondary schools set to increase, it is unlikely that teaching timetables can be reduced if teacher numbers do not keep pace and there is not an increase in class sizes."
Chairman of EPI, David Laws, said: "This analysis highlights that the English education system is unusual internationally in its long working hours for teachers, low levels of professional development, and what looks like a high burnout rate of teachers.
"Combined with relatively low starting pay for teachers in England, these three features of our school system have clear risks for recruiting, retaining and developing a high quality teacher workforce."
The Department for Education said it recognised teachers' concerns and is continuing to work with them to find constructive solutions.
"Teaching remains an attractive career and we have more teachers entering our classrooms than those choosing to leave or retire.
"Teacher retention has been broadly stable for 20 years and the annual average salaries for teachers in the UK are also greater than the OECD average, and higher than many of Europe's high-performing education systems like Finland, Norway or Sweden."
Toilet break or marking
Teacher Anita Smith moved to a primary school hoping to lessen the work load, which it did slightly, "only because my job role has completely changed".
Many of her primary school colleagues tallied up their total hours to almost 60 hours a week.
"I don't think primary school teachers have it any easier," she said.
An average day for a teacher, according to Ms Smith, is getting in between 07:30 and 8:00 BST and not leaving before 17:00 or 17:30 if you have a "lucky" day or are going to an appointment.
What you do not do in school you take home, and the same over the weekend. You clock up four to six hours after work, she said.
She said: "We take professional pride in our work, we want to plan great lessons, we want to give great feedback, meaningful feedback to help our students make great progress."
Deciding between going to the toilet during break or finishing off work before the schoolchildren come back after lunchtime is a choice for every teacher daily, Ms Smith said.
When asked about the 12 weeks of holiday, she told BBC Radio 5 live that teachers completely understand that the long holidays are a pay off for the long hours.
But she said the "extreme" hours during term time were causing people to burn out physically and mentally.
Head teachers have a "duty" to make sure their staff have got an acceptable work life balance. She said work life balance during term time "simply does not exist."
The school, in Leeds, Ms Smith works at opens during the holidays because teachers come in and get work done "not for them, but to make sure the kids are making progress and are having the best opportunities in the classroom they possibly can to learn."
Dr Mary Bousted, general secretary of the Association of Teachers and Lecturers, said: "Most worrying is the fact that teachers' professional development is being cut, at a time when there is massive change in the curriculum, its assessment and qualifications.
"Teachers want to do the best they can for their pupils, but they are being held back by 'busy work' and a lack of training and development which would enable them to meet the challenge of change which, for many, is overwhelming."
Kevin Courtney, general secretary of the National Union of Teachers, said: "Teaching has always been a long-hours profession, but hours spent preparing exciting lessons are very different to hours spent providing evidence for bureaucrats.
"The fact that teachers are working 60 hours a week is totally unacceptable and is exacerbating the teacher shortage."