The reason for the restriction is at the 'behavior school' some students were so violent that they couldn't handle going out in public without actually attacking a person or animal. Also, some kids were at high flight risks. There are various levels (we used a color system) that the students are placed at. For example, if they are at level green, they had the least restrictions - they can go out in public, etc. If they have level red, then that's the highest restriction. Most of my kids were red and orange. Some of them had to be restrained to keep from raping me in my own classroom, simply because they couldn't resist the anger of women who probably were the main sources of abuse and neglect in their lives.
So, going to a dairy farm for some of them was too much stimulation. It is hard to control the enviroment (for instance, the farmer might have a pitchfork laying around). However, I knew that they needed the same quality instruction as other kids with special needs. So I had to be creative...and filled out like over 30 pages of paperwork and do some serious convincing on my part...and was able to bring the farm to them.