Apparently, some teachers are concerned that school districts may ask them to sign waivers releasing the district of liability for COVID-19-related illness. The Tennessee Education Association has some advice should that happen:

Frequently Asked Questions Regarding Educators and Coronavirus/Liability Waivers
My district is asking all employees to sign a waiver releasing it from liability related to the current pandemic. I do not want to sign the waiver, but I cannot afford to lose my job, nor do I want to lose my rights. What should I do?
Ideally, members should not sign any sort of waiver of their legal or contractual rights that they do not fully understand and voluntarily agree to without first speaking to their UniServ coordinator or local association leadership for guidance. If necessary, local leadership or UniServ will involve TEA Legal so members can be advised of their rights with respect to signing the waiver before being required to do so.
In the event a directive to sign a liability waiver does not afford an opportunity to have the content of the waiver reviewed by the Association prior to signing, members facing the real or perceived threat of reprisal should consider signing the waiver with a handwritten statement including the following concepts adjacent to their signature:
1) The signature appears as the result of the directive and is not voluntary; or
2) The signature does not constitute consent to the terms of the waiver, nor should it suggest the full extent of the waiver was understood at the time the signature was made.
If an educator is required to sign a waiver and is not provided a copy of the signed waiver, educators should follow up with their administrator via email and ask for a copy.

Here is a waiver from a Florida school district:

If you’ve been asked to sign a waiver and have a copy, please email: andy@tnedreport.com