I'm guessing they are looking at it from a liability standpoint. If he were to bolt in a crowded amusement park... they could lose him or he could get hurt. It's not as safe as the more controlled environment he has at school and I'm guessing they are just trying to cover their butts. I suppose the other alternative would be to not let him go on the field trip. If it came down to wearing the harness or missing the trip, which would it be?

I understand the feeling that a harness is basically a leash, but I feel very strongly that the potential alternative (my son getting away from me and getting run over by a car, getting snatched by a stranger, etc) outweighs any discomfort I might feel about 'leashing' my son. I harnessed him when travelling while I was pregnant - running after a not-quite-two-year-old in an airport is hard work anyway, but doing it with a big pregnant belly is damn near impossible. He deals with it well and I feel better about walking with him in a large crowd where he could easily get away from me - he only lets me hold his hand for so long before he's had enough and ready to take off. Knowing how he is, I would actually insist that a caretaker harness him in an amusement park. The possibility of him getting away and possibly getting hurt is just too great for me to take a chance. However, if your son, unlike mine, actually looks for you and tries to stay near you when you are out and about, your risk may be smaller than mine and you may feel okay about trusting your caretakers to be able to keep up with him.

Just my two cents - use or ignore as you will =-).

My kid is now an adult and still wears a harness on the bus -it is safer than just using the lapstrap.
She knows how to get out of a harness too -she learnt that at 8 years of age but she stays put and I know that if she gets in a collision she will be safer than with just a lap belt. -she used to sit in a car seat on the bus when she first started . Then the tiny harness -I could barely see the top of her head through the bus window. my kid is nonverbal the more safe I can keep her the less the stress. She has been in two bus collisions too in her lifetime and I am thankful she had the harness on.

So his field trip was yesterday. When we talked to the school administrators about it last week, we agreed that they would purchase one of those belt-loop ties. His one-on-one would wear one end attached to her belt-loop and he would wear one on his, and it would draw out like measuring tape, I guess, to give him some distance. Basically, a tether of sorts, but not a "harness". We also agreed that they would start the day with nothing, just hand-holding if necessary, then only move to the tether if he seemed like he might bolt or resisted the hand-holding. That was an acceptable compromise to us. The best part is that they didn't end up using the tether at all. He never tried to bolt, and if he started wondering away, they just called to him, or sent one of the aides to direct him back towards the group, and he was fine. He had a great time, completely harness-free. Yay!