<p>I would also check if any of the homework answers are available in the back of the text. If he’s doing multiplication in his head, it may be that on tests he’s being asked to show all his work, but is just putting down the answer instead. I would also suggest that you watch him do his homework a couple of times to see how he’s coming up with the answers - whether it’s looking up info, using a calculator … I would ask for a meeting with his teacher to figure out why there’s such a discrepancy.</p>