Guaranteed to keep you safe.
You can work proper sneeze/cough etiquette into the lesson. Just make it seem like it is a normal part of learning to play the piano: to be cognizant of all others that use the instrument. Sort of like proper posture at the instrument, there is also a proper procedure when one has to sneeze. Cough into ones arm - get a sticker. Don't touch one's face with hands - get a sticker. I've seen Lysol wipes used on the keys.
HEPA air filter.You're going to be around germs. Get a flu shot (and hepatitis and everything else... TB, too...)Just make disinfecting the piano part of the lessons. A quick wipe down on the keys after each student isn't going to insult people too much. Who's going to argue against that if you say how many people have touched the keyboard that day?Another nice trick -- Sit upwind from the student. If there's a fan that's quiet enough, have it blow from behind you toward the student. That way their germs move away from you. Or maybe the room in the air would just move in that direction anyway. Also helps for a student who has bad breath or BO.Ugh... I remember one kid who spat on his hands and rubbed them together before touching the keys. He was getting ready to work, oh yeah... spit on those hands.... I suppose having Kleenex out, hand sanitizer... That stuff wouldn't hurt either. They could voluntarily disinfect themselves a little that way.Ziacam is supposed to actually work too. The melt drop kind. They coat your mouth with zinc I think so the germs physically can't get in as much. I heard something about that years ago. Might not be work all the time, but it's something.