There are many substitute teachers who willingly worked throughout the pandemic that you will lose if you require the vaccine.  Some of us worked 40-90 days during the last school year.  SCIENCE shows that those who have had the virus have much more protection than the vaccine gives.  Even when antibodies have declined b cells provide adequate protection.  In addition the multitude of breakthrough cases is increasing daily.  The spread of COVID is not decreased by having the vaccine.  The only consequences of not having the vaccine is to the individual.  There are no long-term studies on the effects of this vaccine.  After it has been proven to have no deleterious side effects in 10-15 years, then you might consider a mandate.  Until that proof exists, the vaccine should be a personal choice.

You will drive teachers and substitutes to other venues than public schools.  As I'm sure you know, such opportunities are increasing exponentially as parents take control of their students' education.  Teachers do not teach for the money; that has never been a driving force.  Teachers teach for the joy of it.  The venue is not that important.

It is in the best interests of all to leave the COVID vaccine a personal decision as the flu vaccine is.  The already declared mandates in other areas should be recalled.  Long-term studies are necessary before mandates.  Look up the FDA approved drug thalidomide.  https://pubmed.ncbi.nlm.nih.gov/21507989/   Then imagine if every pregnant mother had been required to take the drug.