But how much more interesting it would be for teachers themselves to reflect on the common sense answers we already have - thanks to the extensive research into formative assessment by Paul Black and Dylan Wiliam.
Rather than worrying about the uncertain role of setting in raising attainment, their work has pointed towards the crucial importance of involving all pupils in their own learning by giving every one of them a clearer understanding of what they are learning (not just doing) and helping them to recognise their own successes and points for improvement.
Black and Wiliam's research is clear : improving formative assessment raises standards and schools and teachers can do much to improve the ways they use it.
They have also found that improved formative assessment reduces the gap between low and high attainment, so resolving any tension between social inclusion and raising standards. Even better, they took their findings into real schools in Oxfordshire and Medway towns and demonstrated their effectiveness in the classroom.
The main barrier to improving attainment may simply be that too many teachers believe that teaching and learning are just two sides of the same coin.
One effect of this may be a willingness to experiment with setting.
The real challenge of formative assessment lies in its clear focus on learning, and the need for teaching to respond to whatever is revealed by assessment of what has been learned.
Such a fundamental shift in approach is easy to describe, more difficult to achieve. Yet it is essential if real gains in attainment are to be realised.
The answers you seek are most likely to lie with teachers and their own reflections on how they teach.
Eric Young iTelligent Classrooms Mayfield Biggar