[mesmark]

At a conversation school, I think 5 hours a day is probably good. 4 or 6 hours/day is acceptable. (22-25 total hours per week) If you are at an institution that requires other work from the teacher, like research, managing students activities, attending seminars, ... then less hours teaching per day.

It also depends on how much time they have in between.

I'm a private teacher and I get paid for each class that I teach. The more classes, the more I earn. So, I get excited about a work day that has a lot of classes. A salaried teacher won't look at the work week in the same way.