I once taught Higher, Int 2 and Int 1 computing along with Higher Info Systems all in the same class. I inherited the class (new post) so couldn’t really say anything about it, but I told them straight that I would not be doing it again. They accepted my stance.
It is completely unfair on teachers, but more importantly the pupils. Could you imagine choosing a subject to find out that you are lumped in with 3 other levels/subjects?
Teaching that class was a nightmare to say the least (though the pupils were great). It impacts on the learners and that is unacceptable in my view. It will then be reflected in the grades which then reflect on you and that is unfair.
If I were you, I’d tell SMT that it’s impossible to give the pupils a fair shake with that much variety in a single class and that if they force it upon you, they are disadvantaging everyone in the class.