The Teaching and Learning International Survey carried out by the Organisation for Economic Co-operation and Development in 2013 — to examine the working hours of public middle school teachers in 34 countries and regions — came as a shock. The international average was 38.3 hours per week, but by far the highest was Japan's with 53.9 hours, far higher than any others on the survey. The second highest was Alberta, Canada, with 48.2 hours, and the third was Singapore, with 47.6 hours.

What was even more alarming, however, was a survey carried out by the education ministry in 2016, showing that elementary school teachers in Japan worked an average of 57 hours and 25 minutes, and junior high school teachers 63 hours and 18 minutes per week.

According to the survey, 33.5 percent of elementary school teachers and 57.7 percent of junior high teachers are estimated to have clocked more than 80 hours of overtime a month. If the hours that teachers routinely spend at home to take care of their workload, which come to four or five hours a week, are included, 57.8 percent of elementary school teachers and 74.1 percent of junior high teachers did more than 80 percent of monthly overtime — a level of overwork deemed to threaten workers' health.