I have seen a lot of kids quickly pass off their 2’s, 5’s, and 10’s. These tables have an obvious pattern and are much easier to learn. Then there is a serious slow down as kids hit the 3’s, 4’s, and 6’s. By the time they get to the 7’s, 8’s, and 9’s they’ve decided that multiplication is way too hard, and math isn’t their thing.
Children may also get started with money, time, and measuring, though it is not absolutely necessary to master any of that. The teacher should keep it playful, supply measuring cups, scales, clocks, and coins to have around, and answer questions.