"Multiplying-in-columns" is quite out of fashion. A 'grid' or 'boxes' method is surely now taught to/used by a majority of students in the UK. Long multiplication is not considered best practice and many students don't see it.<p>This is thankfully for the better, as weaker students are better able to follow the method and stronger students can extend more intuitively to general distributive methods (making mental arithmetic more convenient).<p>In my opinion, this makes the 12 times table even more irrelevant.<p>Links:
<a href="http://www.bbc.co.uk/schools/gcsebitesize/maths/number/multiplicationdivisionrev1.shtml" rel="nofollow">http://www.bbc.co.uk/schools/gcsebitesize/maths/number/multi...</a>
<a href="http://www.bbc.co.uk/news/magazine-11258175" rel="nofollow">http://www.bbc.co.uk/news/magazine-11258175</a>
Learning it up to 9 is obviously important, unless you don't think being able to do any kind of mental math is useful.<p>But the 10s and 11s are very easy to learn, so there's not much reason to stop before 11. I suppose there isn't much objective reason to include the 12s. They make a nicer endpoint than the 11s, and are no easier or harder than (say) the 6s or 8s, but they don't come in handy nearly as often.
Food items are often dealt with in dozens - eggs and doughnuts, for example. Presumably, most people will end up dealing in dozens of eggs at some point.
One minor confound is that the difficulty of each new fact isn't identical. While going from 10 to 11 requires learning 11 new facts, 9 of them follow an easy pattern (11 x n = nn), and the 10th you get for free with decimal notation. That leaves only 11 x 11 = 121 to be memorized individually.<p>Oddly I don't think I ever memorized the 12 x [0-9] case myself. It's quick enough to recover it from smaller numbers (12 x 7 = 70 + 14) that I just did that in school, and memorized only 11 x 12 and 12 x 12.