I've had bad teachers before, and I've had good teachers before. What I've observed is that the tests tend to prevent the good teachers from being good without really detecting the bad teachers. A few of the best teachers I ever had were forced to waste a month ticking boxes on the "get ready for the test" list, a month that they could have spent teaching things that were actually useful. Meanwhile, the bad teachers went on doing exactly the same thing they were doing before, because even a doorknob could have checked off "students must have studied the following important people from the civil rights movement".