howdy, the possible reason that I think is missing from your list and from your thinking is that teachers are professional educators that are trained in (normal) child development. Our children are outliers who do not really have normal development, so they challenge the beliefs of those who have been teaching professionally (especially for a long time, but even newer teachers can fall prey to this). That's why the "one every fifty or hundred years of teaching" statistic can be so powerful, because it gives them an understandable reason why they should set aside their professional knowledge in considering this particular kid.
