Dylan Wiliam, Michael Toth, Laquita Louie and Paul Zavitkovsky discuss why most current forms of large-scale, standardized test reportage are so difficult to use for improving teaching and learning.. This problem has become more acute recently as a growing number of American states consider replacing conventional, year-end testing with "through-year" designs that roll up results from multiple, large-scale interim tests into a single year-end accountability score.. .