When to go back to work

Started feeling sick on Tuesday, took a test Wednesday night after losing sense of smell, was positive but the test was expired by a few months. Went to doctor and tested positive on Thursday. Stayed home from work Thursday and Friday and rested all weekend. I’m still congested and have a lot of mucus going on. Guidelines say if your symptoms are improving to go back but mask. However, my symptoms have shifted. I’m a teacher and one of my aides has a newborn at home. I don’t want to get anyone else sick, but I don’t know if this is just a post nasal drip or what.