They ask "Are you symptomatic for COVID-19?"
They're not asking for an employee's medical records.
If they say "yes" then they should be quarantined, as per adopted policy by most districts and recommendations by HHS and the CDC.
If they say no, they can follow up with "Are you willing to go get a test (possibly) at district/campus expense?"
If no, or they refuse to answer the first question, then it's either a minor disciplinary issue (refusing to follow district policy) or they could be considered as willfully endangering their coworkers and students - which is a much larger disciplinary issue.
No "medical information" is being transmitted here. "Are you sick. (Y/N)" "Y: Go home." N: You are symptomatic. Go get checked out."
It's the same as coming to work with pinkeye. If you have it, your employer WILL SEND YOU HOME. If you work food service, and come in with the flu, YOU WILL BE SENT HOME. This is NO different.
Plus: this may come as a shock to you, but employers are not required to follow HIPAA guidelines. Per their own website. Link below.
There's no line being crossed. Or if there is, that line was crossed DECADES ago.