Why do this? You put the entire careers of educators in the hands of a few vindictive kids or opportunistic administrators. So much for the bill of rights which supposedly covers you at work as well as outside of it.
This just cinches up the power that the fat cats have over the peonage. They will claim "you can never be too careful." Fine, then why aren't you and everyone in the house wearing a helmet to sleep every night, just in case the house caves in? You wouldn't want to risk anything would you?