It takes from 7 to 10 days to fully recover from the chickenpox and for the spots to go away.
When a person gets infected with Chickenpox the spots usually start to appear 10 to 21 day after being infected with the chickenpox.
If you or a child has chickenpox you should stay home until you're longer contagious with the chickenpox which is usually a day after recovery so I would wait until the 11th day before returning to work or sending your child back to school just to be safe.