Honestly sounds like the teacher is just the uptight type. I personally would worry to much. Seems like normal behaviour to me. My almost 13yr old son still wont tie his shoes or always properly dress for the weather (living in Canada, its often very cold). Not that he doesn't know how. Its just that he cant be bothered and chooses not to. Honestly I used to fight all the time with him about it when he was younger. Now I pick my battles and its just not one I choose to fight with him over. The way I see it, he'll either grow out of it, or learn the hard way (frost bite, etc). Ask the teacher what he suggests you do about it, but I wouldn't stress over it.