I am an ex high school teacher and started off working (at an office job) during radiation. Something to consider - you may not be able to get a regular session time during treatment that will accommodate your classes. I was all right for the first two weeks but after that, the tiredness began. In hindsight there is no way I could have taught during the last few weeks. The body is going through a lot of cellular changes and needs rest. One day I would be fine but the next day the fatigue would just hit me. I ended up working two days a week for the last couple of weeks and had a week off after treatment to deal with burns. If I ever did it again (obviously I can't) I would wait to go back to work and enjoy the down time. But everyone is different.
Good luck with it.
Nadine