And time and again it has been pointed out that there has yet to be devised an accurate measuring tool of the type newspapers and managers are so fond of that do justice to a teachers performance, whether good or bad. There are far too many parts of the equation (a) out of the teacher's control, and (b) that cannot be accurately measured. I have lost the link - but there was a major big article by a professor at Standord University, which explained in detail that these kinds of rankings, let alone the methodology used have little validity, and are a poor reflection of a teacher's performance.
Even more so, way too many people believe in the infallabillity of these numbers - and media as well as politicians and special interest groups have no incentive at all to vouch for their accuracy, since that (a) does not sell (makes not for a simple sensationalist story) and (b) would not suit their purpose, since they have to gain by misrepresentation of not outright fallacy.
We have become - as a society - way too infected by the BS that 'measurement/hard data = knowledge' and that 'everything can in fact be measured'. It is outright lying BS, which infortunately is still extremely dominant, and preached as religion in most management and economics courses. Most people have no f-ing clue what actually is being measured, and what factors in in the results. In fact, more often than not managers and economists deliberately ignore anything that is difficult to measure in their data-collection, let alone when analyzing the collected data, while presenting the results as an accurate reflection of what ought to be measured.