Did all those Wisconsin schools have to close late last week in response to the wildcat "sick out" the unions staged? I'd like to think most teachers are better than this, staying at their post, enough present to preclude physical closure of the buildings. I'm sure there were financial reasons involved as well, but not enough to keep Superintendent Speed from trying to keep my schools open.
I'd double and triple up the classes as necessary, and bring in every substitute in my Rolodex. If some teachers has the temerity to question or complain, I'd tell them to take it up with their missing peers.
Later I'd send specific letters to the parents. "Your child's teacher was among many who failed to report to work last Thursday and Friday. As of yet, she has yet to provide a verifyable excuse or reason for her absence. We apologize for this abbrogation of the trust you place in us. And even though we did what we could with limited staff, we will obviously need to extend the school year to make up the academic time lost ..." And to be fair: "We thought you should know that while you child's teacher was here as scheduled last week, we had no choice but to impose a consolidated class of 68 students on her to cover the as yet unexcused absences of other teachers ..."
Finally, I'd send this to the press: "We have hired Nero Wolfe to oversee an investigation of the large number of medical notes submitted with similar handwriting. We intend to follow through where fraud or breach of contract is indicated, including the appropriate referrals to the state medical authorities."