For all teaching staff, the weekly working hours do not exceed 36 hours, with the legislator setting this norm for 1 rate.

At the same time, according to paragraph 4 of the Instruction on the procedure for forming a model annual work plan for pedagogical specialties of general secondary educational institutions (registration number 3058), the annual workload of a teacher of a general secondary educational institution is calculated as follows:

• By multiplying the weekly workload by a factor of 1 in the amount of one rate established for grades 1-4, i.e.: 18x1=18+18=36x4.3 (week) =154.8x43 (week) =1548 hours;
• By multiplying the weekly workload by a coefficient of 0.8 in the amount of one rate established for grades 5-11, i.e.: 20x0.8=16+20=36x4.3 (week) =154.8x43 (week) =1548 hours.

It should be noted that the above norm applies only to full-time employees.

Therefore, if your lesson is 7 hours, you don't need to be at school all day. This means your workload will be 12.6 hours per week.

So you should be at school for 12.6 hours a week.
It's illegal to ask you to be at school longer than that.