Better math through chess

I've just come across another study attempting to measure whether teaching chess in the classroom results in better learning outcomes for students. In this case the study looked at replacing 1 math lesson a week with a chess lesson (as opposed to adding an extra chess lesson). The study was carried out in Denmark, involving primary aged students.
Overall the study found a slight improvement in test scores (around 0.1 to 0.18 of a standard deviation), which at first might not sound like much. However, as these were replacement lessons, the result is in fact a lot better, especially if you are trying to get chess coaching into an already crowded calendar. Also of interest is that the study looked at the effects on children who were either unhappy or bored and found  that both these groups showed greater improvement than happy or engaged children. In fact most of the improvement in test scores was attributed to students in these groups.
The whole study is available here and is worth reading not just for the conclusions, but also for the description of the studies methodology. In describing quite clearly their approach, the authors not only help the reader understand their work, but also provide an idea of what to look for in similar studies on chess in education.