Extreme burn out in school

I have worked at this school for more than a year now, have worked my a** off, teaching a core STEM subject to 7 sections of middle school. That’s a total of 28 classes per week, which left me little to no time for the documentation work, taking print outs, you know it. This led to the work needing to be finished at home. So yeah, I pretty much did not have a personal life the entire year last year.

Anyway, a new academic year started off today and guess what? They gave me 7 sections AGAIN, AND gave me a tonne of extra responsibilities! I did not feel like keeping quiet this time and asked them why there was so much disparity amongst work distribution (the other teachers have gotten 5-6 sections to handle). All I got was generic answers and asking me to approach the principal and the CEO. Is this fair? Is this how you treat employees here, just because you’re paying their salaries and giving them a visa?

I am STRESSED. I am on the egde of breaking down. The situation is so bad that the minute I enter the school, i do not have the luxury to even go to the washroom, in case I get late for the class and the supervisor gets mad that the class was left unattended. I do not get time to eat lunch because I have duties during lunch time as well.

What do you suggest? Should I just quit this job? Its taking a huge toll on my life. Are other schools in Dubai the same?