This article seems to have the common failing that it never really gets past page 2 of Bloom's paper. Bloom's paper is mostly cited in the intelligent tutoring

This article seems to have the common failing that it never really gets past page 2 of Bloom's paper. Bloom's paper is mostly cited in the intelligent tutoring systems world for it's title and first page (the identification of the problem, which was summarising two of his students' results), but the majority of the paper is spent analysing other interventions, such as improving instructional materials, home environment and peer group, enhancing cues and participation, etc to see how close they can get to matching tutoring. The bigger issue with trying to use the numbers from Bloom's paper today is that "effect size" assumes the control groups are similar. Bloom's studies were in US high schools in the early 1980s. Most ITS papers are on university students or interventions that are also supported with extra staff time and training. They're often on different subjects, with different levels of support in the base class, differently motivated students, different home environments, different teaching styles, etc, but we expect the results between studies to be comparable. I doubt even modern US high schools are like US high schools of the 1970s and 1980s. The control group for Bloom's studies no longer exists. To give an extreme example of this problem - that control groups in education are not at all similar - when I was doing my PhD on AI in education, I was doing it at a university that gives "supervisions" (small group tutoring) to all its students. So if I were to have tried an "effect size" study on anything I built, my control group would have been equivalent to Bloom's intervention group (in that they did receive small group tutoring) not his control group. When I was doing my PhD, I had a little informal tea-time quip which was that the flip side of effect size analysis is everything control groups "don't do" if they're to be comparable. Bloom finds classroom morale has a 0.6 sigma effect, so should we take it that the base is that our studies should take place in classes with bad morale? Assigning homework has a 0.3 sigma effect, so presumably control groups don't do that (let alone mark it because that has a 0.8 sigma effect)?