I LOVED the article I read awhile back about the "motion" standing desks that many districts are using...of course not ours...but it is a desk that allows the students to stand to do their work if they feel like it and then if they want to sit, it comes with a stool and attached to the desk is a swing arm so that their feet can swing at the desk while they work. My DS6 would LOVE this idea.

http://www.nytimes.com/2009/02/25/us/25desks.html?_r=2&th&emc=th