Aufilia--thanks for the link. That makes me feel somewhat better about it.

puffin--i wonder if that's what Singapore Math teaches them to do. I think that's what DS is doing when he multiplies large numbers, like 96X12. But he makes too many errors so the teacher is trying to get him to write it down and carry numbers the normal way. For a kid with good working memory it probably is fine but he is only in first grade and has pretty average working memory so that's probably why it's a problem. I tell him it's fine to do it in his head, but can he please write it the normal way afterwards to check his answer.