I carried on working during my chemo, but that was in an ordinary office of 10 people or so (in hindsight, I was stupid, I should've taken more time off).
In the working environment you've described, personally I'd avoid going into work for exactly the reasons you've described. No point exposing yourself to further unnecessary risks of infection etc, especially given the fact that there will always be new people coming in to your classes.
Your workplace should have absolutely no issues with this, at the end of the day, you're having aggressive treatment for a serious disease.
All the very best with the treatment, too.