Notify the teacher as soon as you know illness will keep the child from her appointment that day. If you call the teacher after you have missed your lesson appointment, it probably will be a forfeit. Teachers will not reschedule for these situations. It is your responsibility to arrange a back-up system in case you cannot transport your child to the lesson. There are many ways teachers handle make-ups not related to the child's illness.
Some teachers allow no reschedules.
Make-ups are allowed for illness, but there are no reschedules. Some teachers allow non-illness reschedules if the teacher receives 24 hours' notice. The great likelihood is that teachers will require that you choose between two conflicting activities if the request for rescheduling does not fall within the teacher's guidelines. This is standard procedure, so don't be surprised that this is so. The teacher has your child's time set aside just for her.