|(from Trailblazers Math, grade 2.)|
Unfortunately, life is not that simple. It is possible to be mentally engaged while sitting quite still (e.g., while watching a movie), and it is also possible to be mentally absent while moving around (e.g., daydreaming while folding laundry.) You can make kids move around, but that doesn't necessarily mean that they're interested in what they're doing, or that they're learning anything in particular. A bad project is less engaging than a good lecture.