When you have chickenpox you're contagious for 2 days before the spots of the chickenpox appear and then you're contagious for up to 5 to 6 days after the spots of the chickenpox appears on your skin.
Wait until after 1 day after the chickenpox goes away before sending your child back to school or if it's an adult also wait up to a day after the chickenpox goes away before you go back to work.