The USA's National Wildlife Federation encourages outdoor learning in school gardens and habitat areas and is active in 8,400 schools.
As such, it is interested in the academic and broader learning effects of school garden programs, and has recently tried to summarise what the research literature says about gardens as a learning asset for schools. It drew on a recent literature survey (Williams and Dixon 2013) which is a summative assessment of 48 studies (between 1990 and 2010) of the various effects of school gardens on learning and other outcomes.
The Federation says this about all this:
“The results of the studies show overwhelmingly that garden-based learning had a positive impact on students’ grades, knowledge, attitudes, and behavior. These positive impacts prevailed for nearly every outcome group, including the elementary, middle, and high school levels, with positive impacts of 85%, 83%, and 91%, respectively, although the number of studies at the high school level was the lowest. The preponderance of overall positive findings is important since research methodologies of the 48 studies were found to be highly eclectic. These findings speak to the potential of garden programs in benefitting academic and academic-related outcomes."
It goes on to make a point that reminds me of the work that Garden Organic did a few years back for the Food Growing in Schools Task Force:
"However, these results also indicate that garden instructional activities may need more curricular development and integration with particular subject areas if they are intended to improve academic performance. Perhaps garden-based learning could serve as one venue to advance the recent interest in education reform promoting Science, Technology, Engineering, and Mathematics (STEM) initiatives (National Science Foundation, 2010) and for career prospects in horticulture, landscape design, and architecture, as well as food, nutrition, and health.”
The Foundation said that, taken as a whole, the advantages of garden-based activities are overwhelmingly positive because school gardens support constructivist learning. It also pointed to three studies:
If only I had the time to read all this; the trouble is, of course, that I'm spending so much time in the garden ...