While we are on the subject of what really matters for human welfare, many people expressed approval of the government’s decision to not allow class sizes to increase further. Kevin Denny has been talking about this issue for several years and basically arguing that the evidence on class sizes is mixed at best and that it is more of a teacher workload issue than a pupil welfare and performance issue. He has just put out a paper with colleague Veruska Oppedisano testing the effect of classsizes on pupil performance. According to his results, bigger class sizes are associated with better performance in the PISA data, even controlling for a wide range of controls and using different estimation techniques. I think Kevin would be the first to say that you should be careful about overinterpreting any individual data analysis but it certainly points away from any simplistic assertions about the effects of class-sizes.