My daughter's big toenail started coming off a few days ago, there is no discoloration and she has not injured it in anyway. It is not painful. I thought she may have bumped it or something and just didnt remember. She is 7, but this evening she said that 3 other kids in another class in her school have had finger nails fall off. Can you please tell me what may be causing this. Her school is an old school dating back to the early 1900's. Other than that i have no other information. Thanks.

Nails don't fall off for no reason. I would take her to your dermatologist for a diagnosis. There is some reason fro this, but if it is happening to others in her school, I seriously doubt if it is something genetic.