Ah, didn't know there's a full coverage by BBC:
http://www.bbc.co.uk/news/uk-scotland-24608813"They claimed that since every 15 minutes of exercise improved performance by an average of about a quarter of a grade, it was possible children who carried out 60 minutes of exercise every day could improve their academic performance by a full grade - for example, from a C to a B, or a B to an A."
But this is an observational study, unlike the intervention studies I linked above. So, bias should be expected.
Edit:
Companion Paper:
http://www.sciencedirect.com/science/article/pii/S1755296613000501Original article is:
Booth, JN , Leary, S, Joinson, C, Ness, AR, Tomporowski, P, Boyle, JME & Reilly, JJ 2013, ' Associations between objectively measured physical activity and academic attainment in adolescents from a UK cohort. ' British Journal of Sports Medicine .
But I can't find the pdf yet.