I've been a chaperone on many field trips. First, four year olds are awfully young for a trip to the museum. That was a waste of time and resources. Second, as a chaperone, I've always had 4 kids that I was responsible for. The article says they had all the adults they needed so someone was really stupid here. Lastly, every trip I've been on, teachers are constantly counting heads. Failing to do this is pretty incompetent, especially with this age group.