My DS8 learned them at the beginning of this school year at 7 years old. He grade skipped and is in 3rd grade this year. He is PG in quantitative reasoning but doesn't do very well at memorizing facts. Two things helped him. First, my DH sat down with him and they drew the 12 x 12 chart and filled in the easy ones first (eg. multiples of 2, 5, 10) and then they talked through the rest of it while filling it in. Second, the Squeebles Times Tables ipad app helped tremendously.