Here we present the potential socio-economic benefits of upgrading the indoor air quality in Danish schools to the level of Swedish schools. The OECD “PISA” score is used to quantify the effects, together with the Danish Rational Economic Agent Model (DREAM). The paper details how improved air quality could result in higher PISA scores, increasing productivity and could lead to a reduction in the duration of education. It also notes how improved air quality could reduce the rate of absenteeism amongst teachers. The report then concludes that improved air quality in Danish schools could result in an increase in the Gross Domestic Product (GDP) of €173 million per annum, and in the public finances of €37 million per annum.