How I Spent My Day Off
With regard to your assessment of public schools. There is something that I think is a little outdated and flawed with your logic. With most states requiring testing in the subject to be taught as a condition for licensure it is very rare for a teacher to be teaching content they are unprepared for. I can assure you the days of history teachers trying to stay one page ahead in the calculus book are over. The Praxis Test or the MTEL (used in Massachusetts) require a very intimate knowledge of the subject material. This would be knowledge that could only be gained through several years of careful study. I have recently attained certification in Massachusetts to teach chemistry and can attest to the depth and breadth of knowledge required to pass the subject test. It is not something that can be done with a 'Chemistry For Dummies' book studied over the weekend. If a teacher passes such a test for certification you can be confident they are qualified and know the material.
What the test cannot show is whether or not the individual possesses the instincts, patience or charm to connect with the students in the classroom. These are skills that cannot be taught in Ed Schools. There is only one test for those qualities. It begins with the first bell on the first day. It ends when the individual leaves teaching. How the individual leaves teaching is really what bothers many who don't understand the profession. Tenure is not a bullet proof suit of armor. Poorly performing teachers can lose their jobs. It just takes longer to remove them and must be carefully documented.
What tenure does protect is the teacher who has a bad year. The dynamic didn't fit. You can't force 30 students to get along. If they don't behave themselves no learning can take place. If the teacher can't fire the student who is a chronic disruption then the school can't blame low test scores on the teacher. If the town suddenly cuts the budget needed to teach certain courses is it the fault of the classroom teacher? In both cases tenure protects not only the individual teacher but the school system as well. Those intangible skills that lead to effective teaching like patience or charm that are honed over several years are not easy to replace. When students come in and see all new and very unseasoned teachers they will pull every stunt in the book to get out of doing the real work of learning. They will not respect the school or any teacher in it. When students see a school that functions as a cohesive and well practiced team the students respond positively and the teachers can spend their time educating.
Students are the only consumer group that demand less for their money. Throwing money at teachers would be nice but no amount of money can make up for a school system that is continually hiring unseasoned teachers because it has the reputation of having undisciplined students because the school has the habit of replacing teachers who had a bad year because there were so many new teachers the year before and the students took advantage of the many inexperienced teachers throughout the whole school system. (yes it's a run-on sentence) It's a cycle that can only be broken by giving the teacher the confidence that comes with job security. Tenure is the best path to that kind of security.
Blaming the teachers for poor students isn't entirely fair. If a student can't calculate the velocity of a cart rolling down a track, is that the fault of the 20 year veteran physics teacher or of the new algebra teacher the student had the year before? What if that new teacher was only attracted to the job for the money because the town was desperate for math teachers and was allowed to offer twice the salary that an english teacher would get? What if that new math teacher had a class that simply could not behave because the administration had no choice but put a pair of students who've fought each other since middle school into the classroom. Do we need to fire that physics teacher because he had a class of students who couldn't pass the science MCAS after he lost a month worth of the school year reviewing basic algebra instead of teaching physics? This is exactly what tenure protects against.
I don't doubt you're a fine educator at the university level where students are more motivated and personally invested in their education. I do respectfully question your familiarity with the behavior of children whose only motivation to come to school is that their parents drop them off there every morning. I wonder how you propose to correct poor behavior with a revolving door to the teachers entrance.