Sitting is not morally better than standing.
Sitting is not morally better than pacing.
Sitting is not morally better than wandering.
Sitting is easier for some adults to handle than standing, pacing, or wandering.
Why are we more worried about what is easier for adults to handle than what makes it easier for children to focus? Why not spend time training adults about how to work with children who are standing, pacing, or wandering instead of training children to suppress their innate self-regulation abilities?
