For you to assume that a classroom teacher and the classroom itself can be evaluated in the same way as performance in a private-sector job is astonishingly short-sighted.
Every school year, teachers must manage a variety of variables that do not always reveal themselves in a neat, concise, predictable fashion. Nutritional and sleep issues, mis-use of digital gadgets, disciplinary problems, weapons - these and more are what many teachers must handle, day in and day out. Combine these factors with infantile parents who think that the school is solely responsible for their kids from 7 - 3, and teaching really doesn't seem that attractive. Finally, take the sneering and scorn heaped upon teachers as of late, and we all see why a full 50% leave the profession in five years or less.
Measuring competence requires far more than what currently is put into practice. Unfortunately, taxpayers like you are unwilling to foot the bill.
Really - you are your own worst enemy.
How are the rest of us to know that you are a law-abiding citizen? Because you say you are? How are the rest of us to know that you will never go off the deep end and use your gun accordingly? And why is the Second Amendment relegated to guns only by you, when the language says "arms"? Repeal the Second Amendment NOW. TODAY. End this hate-filled fright wing nonsense already.