We've tried providing wood blocks for students to use under their feet as well as changes in how or where their monitor is compared to their eyes. The biggest problem is having parents complain that we should NOT be worrying about how students sit compared to their computers. I heard so many horror stories from the keyboarding teachers that I decided feet on the floor would not be a fight I got into. We focus on proper hand and head placement in comparison to the keyboard and monitor. I explain to students how we can prevent sore wrists and necks by proper laptop placement. I've found by focusing on the laptop and where it is placed, I do not have parents complain about me telling their student how he or she should sit or where their hands should be.
I get my Middle School student's attention by discussing the sore neck that one experiences when a neck is at a weird angle at the movie theater. I ask students if who sat in the front row. Hands go up and I ask if after the end of the movie they have a slightly sore neck. Most quickly say YES! Then I ask who likes to sit at the back right of the theater - again there are many positive responses. Several of these students also say they get a sore neck after the movie. I finish by asking who likes to sit at the back left side of the theater with the same discussion points. I ask students to tilt their heads up and feel the stress at the back of their neck - we then do the same looking to the right and left (like in the theater.) I finish by explaining how this relates to proper computer screen and keyboard placement compared to the eyes. My middle school students seem to grasp the idea and I find I usually only have to explain it once to the entire class. (Perhaps this is because my students experience the sore neck that can come by a twist in the neck during the demonstration.)