Teachers are no different from others in the general work force; they get sick, go whacky, forget why they were hired in the first place, etc. So, they should be treated in the same manner as others in the work force--evaluated against the expectations for which they were hired.

The poor teachers don't deserve protection by their union, nor do they deserve reassignment, etc. If they can't/won't do the job, they have to be fired...same as for others in the general work force.