Which brings up a couple of questions. 1: What were the unions so worried about? and 2: Does the way we're measuring teacher effectiveness make any sense at all?
I have no doubt at all that effective teaching correlates to student achievement. This introduction to a 2005 book explains why teacher evaluation can nevertheless be so difficult to do with any validity. NYS is applying multiple modes to their teacher assessments, as the authors would recommend, but the results simply defy logic.