Unfortunately, as an at-will employe, your wife's employer is free to change the conditions and terms of her employment (such as requiring that she meet a quota) at any time for any reason with or without prior notice, as long as this is not a legal violation or a violation of public policy.
This stems from the employment at-will doctrine, which is codified in California Labor Code Section 2922, and states:
"An employment, having no specified term, may be terminated at the will of either party on notice to the other. Employment for a specified term means an employment for a period greater than one month."
Unfortunately, while the school's policies in having quotas appear to be unethical and immoral, they are currently not illegal nor would they
be likely to considered to constitute violations of public policy.
That said, your wife would probably have an up-hill battle proving that she voluntarily quit for 'good cause,' which is definied as a reason
that would make another reasonable person in the same circumstnaces who wanted to stay employed also leave his or her job.
Still, it is a possibility, but I want to be realistic with you about her chances of receiving unemployment if she were to resign from her job.
To read more about establishing 'good cause' for a voluntary quit, she can read more online here:http://www.edd.ca.gov/uibdg/Voluntary_Quit_VQ_5.htm