Evaluate them on something other than just showing up for work? We love to blather on about how important teachers are yet we don’t hold them to any standards. Standardized test scores? Parent surveys? We just assume they’re doing their job effectively?
let's DO talk about evaluations and WHO should be performing them.
you posted that it is the union's responsibility to do so
that tells me you are unacquainted with labor law
those teachers' unions are OBLIGATED under federal law to represent the interests of the TEACHERS
it would make no sense for the same union which is obligated to represent the teacher in a disciplinary matter to also be responsible for bringing the charges AGAINST the teacher relative to a disciplinary matter and/or one having to do with performance
it would then seem that your argument is misplaced against the unions. you should instead be wailing against the failure of management to do its well paid jobs to identify inappropriate staff issues and then building a case that can effectively demonstrate that a case is there to be made
once that is in effect against the teacher it will then be time for the union to fulfill its fiduciary duty to represent the teacher facing the management allegations
if management fails to make a compelling, documented case against the teacher, management's action will probably (hopefully) fail
despite those above corrections made regarding your post, and who should do what, i agree with your presentation that teachers SHOULD be held accountable. so too, should management. the union should not be needed to perform management's job