I worry, too, about the effects of paranoia in our society at large. Because I automatically had two kids, taking a troupe of 4 or 5 kids was no hassle. I grew up within commuting distance of Boston, so travelling there was no big deal. Museum memberships at the time included parking, so we had memberships to Boston's Science Museum and Children's Museum (and the Fine Arts for awhile, as well). For many adults in this town (about 35 miles from Boston) planning a trip to Boston equates to travelling to the moon - it would never happen for their kids. I never thought about permission slips. In the museums, I pretty much let the kids wander. We visited often enough that my kids knew them pretty well, and they usually had a great time visiting their favorite areas with friends. As far as I know, no guard ever questioned them about my presence (or, rather, lack of presence). If there's a threat of arrest for a parent in a similar situation now, that's more than sad.