The Montessori schools and the Rudolf Steiner schools also teach knitting to very young students. My 6-year-old granddaughter is learning the knit stitch at a Montessori school in Florida. If you can speak with directors at local Waldorf, Steiner and Montessori schools you might get some firm documentation as to how knitting helps children learn.
I have heard that teachers in these schools find that knitting helps calm kids and teaches them to concentrate -- useful living skills in this jumpy, sound-bite, over-stimulated world. (I just glanced at the column of Smilies next to the window where I'm writing this. All the images are jumping, wiggling, jiggling, bouncing -- exactly what kids get when they watch TV or play computer games. Need to knit something and calm down.)