The first real table
Two is doubling and ten adds a nought. Three is the first table where there is no move to make — the answers have to become familiar. That is why it feels harder than the 4 table to most children, even though the numbers are smaller.
A check that always works
Add the digits of any answer in this table and you get 3, 6 or 9. Twenty-four gives 2 + 4 = 6. Twenty-seven gives 2 + 7 = 9. If a child answers 3 × 8 with 26, the digits add to 8 and the answer is wrong, and they can see that for themselves.
Counting in threes is not the same as knowing it
A child who chants three, six, nine, twelve can reach 3 × 7 in about four seconds. That is a useful skill and it is not the table. The missing-number round is the test that matters: 3 × ? = 21 cannot be chanted through quickly, and a child who has really learned the table answers it as fast as the other rounds.