R.M.
According to an AARP website....(strange that AARP would care about Chicken pox...lol)....When someone becomes infected, the pox usually appear 10 to 21 days later. People become contagious 1 to 2 days before breaking out with pox. They remain contagious while uncrusted blisters are present.
so...keep em home until they are all crusted over...yeach