Teachers at elementary and secondary schools averaged of 95½ hours of overtime last October, up 10 hours from a decade earlier, a teachers' union survey said Thursday.
The poll by the All Japan Teachers and Staff Union, known as Zenkyo, covered teachers with regular and postretirement jobs, drawing 5,880 responses.
The poll also found that about 73 hours of OT were logged at school and the remaining 22½ at home.
Junior high school teachers posted the most overtime, at 114 hours and 25 minutes, followed by teachers at full-time high schools at 100 hours and 47 minutes, and those at elementary schools, at 94 hours and 21 minutes.
"In addition to becoming busier with student guidance and dealing with parents, working on the weekends is pushing up overtime," a union official said.
The overtime was mainly logged for extracurricular activities, class preparation, writing reports and meetings.