An essential part of Assessment for Learning is giving feedback to students, both to assess their current achievement and to indicate what their next steps should be.
Feedback is also ranked as the number one intervention strategy in terms of its influence on learning by both Professor John Hattie and the Educational Endowment Foundation: in other words, their wide-ranging researches show that improving the quality of the feedback that is given to students has the biggest impact on learning of any classroom intervention. Improving the quality of feedback can also lead to the greatest levels of progress amongst students. Indeed, the EEF suggests that quality feedback can add 8 months of extra learning. Hattie, meanwhile, says that feedback has an effect size of 0.73. To put that figure into perspective, the average effect size is 0.4 and the highest is 1.2.