Dylan Wiliam in the News

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Benjamin Bloom and the Two-Standard-Deviation Effect

By Dylan Wiliam In a 1984 paper, Benjamin Bloom reckoned that one-on-one tutorial instruction had an impact of two standard deviations on student achievement, but this claim is meaningless unless the sensitivity to instruction of the measure of achievement is specified. For example, standardized tests such as NAEP or TIMSS are relatively insensitive to instruction. […]