Without seeing the animal I can’t guess as to the source of these “bubbles”. As a teacher you now have to deal with setting an example for the children in your class to teach them how to take responsibility for their pets, this can be a valuable lesson. You must find a veterinarian who specializes in the care of amphibians and let him or her examine the animal and advise you as to the proper course of action. Teach your kids that we should not own pets unless we are prepared to invest the time and money required to keep them healthy. If there is no qualified vet nearby who can help you, the lesson is that exotic pets are less appropriate than dogs and cats for whom veterinary care is generally available. Good luck.