But what is teacher quality? How can one measure it reliably? An analysis is issued on a sample of data from a Texas school district. Experts argue convincingly that teacher effectiveness should be measured by students' gains on standardized tests: Mr. Smith is probably a better teacher than Ms. Brown if his students consistently improve their test scores more than hers do. Though this approach is appealing, there are tricky issues. For example, what if Ms. Brown teaches in a school where students score so high there is little room for improvement? The authors try to correct for this problem, as well as other sorts of measurement issues, to generate a measurement of teacher effectiveness. The paper is primarily concerned with how this measure is related to other observable characteristics. The first finding is that there is a large variation in teacher effectiveness: some teachers consistently have a larger impact on their students' achievement than others. Second, easily observable characteristics like having a master's degree or a passing score on the teacher certification exam are not correlated with teacher effectiveness. Then what does matter? The most important single influence is experience: first-year teachers are much less effective than others. The second year is significantly better, and by the fourth year, _ . It is not entirely clear whether this experience effect is learning by doing (the more you teach, the more effective you become) or survival of the fittest (those who are not good at teaching tend to drop out early.) From my reading of the paper, both effects appear important and there is no simple answer. The data do suggest, however, that teacher effectiveness is pretty clear by the end of the second year, so the information to make an informed decision is available at that time. The authors also investigate the contentious issue of racial matching of students and teachers. Here they find strong evidence that minority teachers tend to be more effective with minority students. Again, it is unclear whether this is because of a role model effect (students respond better to a teacher of their own race) or an empathy effect (teachers empathize better with students of their own race) or something else entirely. The authors also look at teacher mobility. There is some evidence that teachers who quit teaching or switch schools tend to be below average in effectiveness. This is consistent with the survival-of-the-fittest model. The author of this passage holds the view that   _  .
teachers will perform better with time passing ineffective teachers should leave earlier rather than later teacher's effectiveness is apparent after a couple of years a master's degree will improve teacher's effectiveness