The first question to ask is, How effective is feedback? We answer this question
by referring to the usual effects of schooling on student achievement and then
comparing them with the evidence related to feedback. Hattie (1999) reported a
synthesis of over 500 meta-analyses, involving 450,000 effect sizes from 180,000
studies, representing approximately 20 to 30 million students, on various influences
on student achievement. This analysis included more than 100 factors influencing
educational achievement and covered various aspects of those typically