How do we get away with this?

We are missing teachers this year.

Two in each of the main subjects: math, science, English, social studies.

Kids have to have 4 courses in each of these subjects, so there aren't a lot of extra classes - they are all required.

Because of the missing teachers - missing for a variety of reasons - some classes have been collapsed, pushing the student numbers higher. And some classes are being taught with subs. And some classes are being taught with teachers with interim or waived certificates. Roughly 10% do not have clear, renewable certificates.

I know they have had the option of rehiring retired teachers, but they wanted these as subs not teachers and the people chose not to do that.

How is this in the students' interests?