Work of teachers

I am surprised to read that our teachers work 46 hours a week of which only 18 hours are spent on teaching and the other 28 hours on administrative and school activities.

Teachers in the other countries participating in the OECD survey worked an average of 39 hours of which 21 hours are spent on teaching and 18 hours on other work.

Why do our teachers have to spend so much time on non-teaching work, i.e. 10 hours more than teachers elsewhere?

https://www.todayonline.com/singapore/singapore-teachers-working-fewer-hours-still-more-international-peers-oecd-survey