A defense of seniority?

Here is a commentary from Schools Matter that appears to be a defense of seniority.  It's funny, but the defense of seniority is often linked with a defense of experience.   As if the two were somehow the same concept.   Teachers improve with experience.   Research confirms a correlation.   This is therefore the best way to compensate teachers or to make hiring and firing decisions.  It's an akward argument to me.... like a person arguing that because IQ is correlated with better teaching, we are therefore simply going to measure IQ and compensate accordingly.   From the article:

 The Times mentions, in passing, that "seniority is largely unrelated to performance." The research on the impact of seniority that I have seen is based on the use of standardized test score improvements, otherwise known as value-added measures. Nevertheless, the results are interesting. In an interview (The New Advocate, "Teacher seniority under fire "September 12, 2010), researcher Michael Hansen said that improvement between year 3 and 25 was four percent, which he regarded as "trivial." But if valid, it means that more experienced teachers are slightly more effective. The only reason to ignore seniority as a criterion for retention in hard times is financial.