The three Rs could soon include “renewable” if Massachusetts has its way. Concerned about rising energy costs and student health, the state is offering financial incentives to districts to build environmentally friendly, health-conscious “green schools.” Through a partnership with the Renewable Energy Trust, districts are being encouraged to make use of technologies, such as solar heating and natural lighting, that simultaneously save on energy bills and make schools better environments in which to teach and learn. The move is part of a national trend to improve energy efficiency in public buildings. That trend could be particularly appealing to educators, says Jeff Wulfson, associate commissioner for school finance with the Massachusetts Department of Education, because “[a]nything you spend on oil bills and gas bills is money you are taking away from the classroom.”