I typically only exclude when the actual child is symptomatic ~ there is a chance that the other sibling WONT get it however I remind parents to be on 'standby' to get here ASAP if the second child develops symptoms so if one is home with a sick child the other parent better be prepared to drop everything to get here ~ typically when you remind them THAT than they just keep the sibling home 'just in case' cause they do not want TWO parents having to take sick time