Ok well in my contract it states that if a child is prescribed antibiotics then they are excluded for 48 hours after the first dose to allow the meds to kick in. Most if not all antibiotics / penicillin take 48 hours before they start to work. So since croup is highly contagious I would not allow her back till Thursday morning at the very earliest depending on when the first dose was administered .... If it was at noon say then Friday morning she would be welcome back