I don’t work in a school but in an open plan office where germ sharing can be quite intense. I was fine. If you haven’t started treatment, the big question may not be exposure to germs but how you react. Fatigue and nausea can make work very difficult. If your job allows, can you make this decision when you know how well you tolerate treatment? Practising putting yourself first is certainly worth doing, but continuing to work may be part of that exercise if you love your work. Many of us had to put planning on hold - bc and treatment often require decisions when and if something happens (or doesn’t happen) rather than carefully planned strategies - which may ultimately prove impossible or unnecessary. Try to do what you most want - but be prepared to shift tack if it proves impracticable. Best wishes.