Natural light plays a great role on mood, no matter the context. It is no different for learning spaces. We know that natural light positively affects our mood, and that positive moods have a positive effect on learning. In fact, it is easy to find tons of researches that are focusing on how to better design new schools in order to integrate as much natural light as possible. The effects of natural light seems to be at their maximum when the classroom has a view on green space, natural grass and natural trees, as it contributes to eliminate the feeling of being in a confined space. But one must be careful to not eliminate the benefits of large windows by painting the nearby walls with dark or agressing colors; doing so creates an unpleasant visual contrast. Keeping walls and ceilings lights helps maintain the feeling of openedness. Other characteristics that could accidentally reduce the benefits of a bright classroom: having a small classroom, overcrowding the space, or making the room visually crowded by using too many colors and posters.
In sum, it appears that the ideal learning environment is a large classroom, free of cluter - physically or visually - with lots of natural light, calm colors, and that offers a view of natural elements. The space should be inviting, yet "plain" enough, that children feel like they can make their own creation in there.