This article examines the argument that "green" schools enhance educational performance. Having set the context of the relationship between environmentalism and the design of schools in the twentieth century, the article explores the performance of a number of green schools built in the UK between 1980 and 1995. The aim is to discover whether attention to environmental or ecological design produces measurable benefits in terms of learning levels in the classroom and the general performance of the school. The focus of the research is upon two clusters of green primary schools built 1980-95 by the local education authorities in Essex and Hampshire. In order to undertake the evaluation a methodology is proposed with criteria established for what design and construction characteristics constitute a "green" school. Key performance indicators available as a consequence of OfStEd inspections, SATS results, teacher turnover and pupil absenteeism rates are used to assess the performance of the schools in educational terms. Central to the hypothesis is that good environmental design leads to enhanced educational performance by pupils and improved productivity on the part of teachers. The methodology consists of comparing the performance of green schools with that of orthodox schools which share similar characteristics of size, location and socio-economic features, and then relating variables of educational performance to design features. Three initial findings are highlighted: first, the importance of classroom daylight levels to learning; second, the benefits to the school of secondary sun spaces; third, the need for attention to the relationship between ventilation and acoustic control in open-plan solar schools.