Could Judging Teachers by Test Scores do Harm?

I'm sick of the discussion over the NY tenure law but, for some reason, I can't resist chipping in another two cents worth of thoughts. I've already written twice (here and here) that I can't see much utility to using the test scores, in their current form, to decide on teacher tenure in NY -- so I won't harp on that again.

NYCEducator argues that the scores are not needed to tell which teachers should be let go, while Kevin Carey fails to see the harm in including the scores in tenure decisions.

If it turns out that the scores provide even a snippet of useful data (which is debatable) then I'd agree with Carey that it also wouldn't do much harm to include these scores in decision-making about teacher ratings (and, hence, firings). But lets turn to a different side of this that I haven't seen anybody address. I've already argued that not using them does no harm, and I think Carey's arguing that using them would also do no harm. We can argue all day over whether the test scores will provide any useful knowledge, but let's think about whether using them could do any harm. Since I'm in the middle of finals week, I'll choose the most intellectually flabby way possible to examine this question -- a game of what if.

Imagine that schools in NY started using the test data (which is questionable in accuracy and only covers 3rd-8th grade Math and English):

What if this were used as the primary way to evaluate teachers instead of a supplemental one?

What if Math and English teachers were scrutinized more closely than teachers in all other subjects?

What if upper-elementary and middle school teachers were scrutinized more closely than other teachers?

What if a good teacher had artificially low scores?

What if a bad teacher had artificially high scores?

What if a teacher had high test scores but abused students?

What if we let gym teachers do whatever they want while we closely monitor other teachers?

What if that gym teachers (not to pick on gym teachers), while we're focusing on other teachers, takes advantage of a student?

What if we forget to monitor serious breaches of ethics because we're so focused on test scores?

What if a teacher cheats on the tests but cleverly enough so as to avoid detection?

What would happen if the hadn't passed is really just speculation, but it's entirely possible that using these test scores to evaluate teachers could have unintended consequences -- and severely hurt students as result.