I didn't want to hijack the other post too much.
Both my DH and I were cracking up over your field trip experiences. When I chaperon one of my own kids' field trips, I consistently get stuck with any nutjobs whose own parents aren't able to chaperon that day because the teacher knows full well that I am also a teacher and that I can probably handle it. And they're right. At this point, I have probably handled more field trips than my kids' teachers have.
Many is the time I've longed to stroll through the zoo or an art museum with my DD and a few of her quiet, bookish girlfriends. Never seems to happen, though.
The really fun part about field trips where I teach is trying to keep kids from eating stuff they're not supposed to eat while out and about. Some families at the school keep kosher while others do not. So the rule on field trips is cold dairy foods only, if a kid wants to buy food. Sigh. I've liberated quite a few cheeseburgers from their owners in Merchant Williamsburg and downtown DC.
The highlight from this year was when one of my 9th graders mouthed off to and provoked a belligerent/drunk homeless guy into a rage in front of a theater in Dupont Circle. No IEP to justify this kid's lack of impulse control. In her case it was plain 14 y/o stupidity. I managed to pacify the offended street person and hopefully conveyed to the kid just how idiotic she was. Oy.
Good times.