“… formative assessment does improve learning. The gains in achievement appear to be quite
considerable, and as noted earlier, among the largest ever reported for educational interventions.
As an illustration of just how big these gains are, an effect size of 0.7, if it could be achieved on a
nationwide scale, would be equivalent to raising the mathematics attainment score of an
‘average’ country like England, New Zealand or the United States into the ‘top five’ after the
Pacific Rim countries of Singapore, Korea, Japan and Hong Kong.” (Beaton et al., 1996, Black
and Wiliam, 1998, p. 61)