Caution on Education - NYTimes.com "Advertisements for the Common Core" (editorial, Nov. 20) cites recent test results as evidence that the new "challenging" national curriculum and "tough" teacher ratings work. Long experience should have taught us all to be skeptical about early claims of educational success and failure. History shows that they often turn out to be overblown or illusory. Furthermore, because of the many variables involved, research in the field is very often equivocal; even as Secretary of Education Arne Duncan declared this latest victory, reputable scholars had started to argue over what the data really mean. Today's education reform policies are a vast experiment. While the Common Core may turn out to be a step forward, there are plenty of reasons to be cautious about its presumed benefits, as well as about the efficacy of the latest vogue in teacher evaluation. Meaningful school reform is a highly complex human task. Good policy depends on a clear understanding of what we really do know and what we don't. We need more thoughtful analyses and fewer premature judgments about what works. MICHAEL V. McGILL Superintendent of Schools Scarsdale, N.Y., Nov. 22, 2013