For the past two years, I have my students do a school report card evaluating how good of a job our school is doing in certain environmental areas.  (energy, resource consumption, erosion, purchasing, biophilia....) This year, we are going to do this at the start of the year (rather than on earth day), and we are going to use the data that we gather to drive our action steps.  I have lists and lists and lists of project ideas and things that we can do, but I want this to be more student centered.  I want them to come up with ideas that they feel are valuable, in areas that they think we could use improvement. 

So I think i will have them: do the report card, determine the area that they feel we need to improve in (biggest need?  most area for growth? easiest to address and change?), propose a plan, and implement *their* plan.  My job will be to guide them and to provide support/structure along the way, but they will develop the action steps that we take.