You will get much more out of your lessons when you are back to feeling 100% because you will be able to give 100%. If your body can only give 50%, you can only expect to get that much at most out of your lesson. Stay home, take whatever remedies make you comfortable and get well. Lessons will still be there when you are better.
I am in the same situation here. Been sick since last Sunday. Missed half a day of work Monday, cancelled lesson on Monday, worked Tuesday and Wednesday, sick again Thursday, cancelled Zumba class Thursday and still haven't lost my cough or headache from last week. Lesson is scheduled for tomorrow evening, but I think I will have to cancel AGAIN... Feeding my horses in my own yard is about as much as I can do right now and even that leaves me breathless. I cannot imagine trying to ride in a lesson. Colds and flu suck!!