waivers for groups, like schools and b-day parties, etc

Hello,

I am just wondering how people in the US are handling waivers for groups, especially schools. Do the students need to have a waiver signed by their parent or guardian, or can the fill out a group waiver when they get to your facility?

I have just moved back to the US from New Zealand, and there we just had all the students sign a group waiver at the facility and the teacher signed the top. I am just getting my head around how to handle that in Wisconsin.

Thanks for any input.

Clay