When can you say it is too much?

When can you say it is too much?

I'm a head of department at a large international school in India. I have a team of eleven teachers I manage. I also still teach three and a half classes and 3 preps. This year, the leadership above me have put extra responsibilities on my job. I have to arrange cover for all absent teachers in my department. I also have to supervise and manage my team for parents conferences that happen every few weeks this year.

My classes are also especially large. In International Baccalaureate (IB) schools classes are usually capped at 18, but I have two classes far above that at 22 and 25. This mean overall I have 80 students to teach and grade. This is more students than I have ever had before in this position.

I'm drowning. I can't do all the administrative work given to me and properly teach so many subjects and students. I work evenings, lunch and on weekends just to stay afloat and it is not working. My two school age children and husband are all suffering from the high stress of my job this year.

My question for the community is this: when can I go to my leadership (bosses) and say it is too much? Does it look unprofessional for me to express how difficult this year has been? I dream of taking more leadership roles, but if I say my role now is too much will I lose these possible future opportunities? I don't know what to do.