Legal Question in Business Law in California

California law prohibits releasing liability before it happens. Calif. Civ. Code sec. 1542. In the case of ultra-hazardous activities, however, California law does acknowledge assumption of risk, including the risk of other parties' negligence. Therefore you are far better off preparing a list of hazards and risks particular to your class and the activities in it, including that you and others may act carelessly or negligently by accident and harm to the students could result, and having people sign off that they have read and acknowledged those risks and are freely choosing to proceed anyway, than using any form release that won't stand up in court. I have never come across a case upholding a form release signed before the accident, but there are many cases where a "release" that contains an acknowledgement of the risks has been found to be an assumption of the risks in horseback riding, scuba diving and river rafting contexts.