Here's me on a school rail- the rail was super sticky and the school has been closed down for a few years.
Here's a famous rail in Edina MN that's at a school, people just hit it on weekends, there's a lot of kids sledding there and they get stoked when they see people hitting it. I don't think I've ever heard of anyone getting kicked out.
Also, there's that weird pyramid urban feature that level 1 hit in eye trip that's at a high school, they just hit it at night. Moral: nights or non-school days for school urban