I don't think I remember actually being taught how to write in primary school. I think they should reteach grammar in high school from the beginning. Most people's brains just can't pick up a systematic treatment of some of the finer points when younger. I went and did all the grammar quizzes over at http://grammar.ccc.commnet.edu/grammar/quiz_list.htm a couple of years ago. It improved my writing a lot, and only took a weekend.