The vaccines employ new methodology/technology. It is impossible to know long-term effects of the vaccine on humans until sufficient time passes. We may think vaccines are safe; we hope that they are safe. BUT we just don't know with absolute certainty. We can see current effects of the vaccines; we can extrapolate future likely outcomes, but we can't be sure. Not until time passes. Medical science has encountered unexpected long-term effects of medical treatments in the past...ones that were believed by many to be safe, effective, wise treatments.  We should not MANDATE that educators and an entire generation of students become part of what is a medical gamble. We think the odds favor vaccination, science may suggest that, but it is still a gamble at this point. The next generation (and the teachers who care greatly for them--vaxxers or antivaxxers both) should be allowed to decide for themselves which odds they choose. Sometimes the dark horse is the right bet against all odds; sometimes the favored horse stumbles in the last leg of the race. It is smart to have a second horse in the race.