Oh no, I totally understand how worrying it is to get a message like that from the teacher out of nowhere! It is really hard to tell just from a photo, so I would bring your child to see the PD as soon as possible, just to be safe. If it does turn out to be chicken pox, the PD can advise on whether your child needs to stay home and for how long. Better to get it checked properly so you have peace of mind, and the school will likely need a memo anyway before your child can go back.