SD is almost 7 and has been brushing her own for a few years now, but like with a lot of things the past year or so, she will do a weak job of it, or play around, spit water all over the place, and generally make me want to scream, so we have to monitor her and I've occasionally had to step in and help her brush so that it's done right. She used to be so gung-ho about doing things herself, but the past couple years has regressed to not wanting to/pretending she can't do things. This goes for a lot of things, not just teeth brushing. One night she made a big act of not knowing how much toothpaste to put on the toothbrush, and acted as if she had no hand-eye coordination trying to put it on, then the next night forgot her act and did a picture-perfect job of it. I don't know if this is "normal" for the age.