Good question caffeinated
Certainly DDs school seems to only teach to x10.
I learned to x12 - but like the reasons cited by mrz assumed it was linked to converting inches to feet - a lot of us oldies made clothing back then, sewed curtains, made quilts, etc...
interesting that x13 is tested for on 11+ - I didn't know that.
I suppose the question is whether schools are teaching that multiplication is multiple additions? And whether our children are getting this? (I don't doubt it's being taught, but the message isn't being received in our case at least - although learning times tables to songs seems a great success and didn't exist in my school days, although the phonograph did)
In principle one can presume that most children would be able to do x11 to at least 11 x 10 - just because they know their ones table. Whether they know the trick beyond 10 x 11 or not is not clear:
beyond 10 to 99 - take first and last digit of multiple - and make a space between - add first and last digit & put the sum into the space. If addition is > 10 - then carry over to hundreds column (etc as appropriate).
so 11 x 11 = 1 - 1 = 1 - (1+1) - 1 = 121
11 x 12 = 1 - 2 = 1 - (1+2) - 2 = 132
11 x 13 = 1 - 3 = 1 - (1+3) - 3 = 143
and so on...
11 x 29 = 2 - 9 = 2 - (2+9) - 9 = 2 - (11) - 9
= 2(+ carry the 1) - 1 - 9 = 319
I like twelves because I still work in inches or dozens
I like 13 because I've always enjoyed a baker's dozen.
So I suppose what we need to double check as parents is that our children could quickly work out more complicated multiples (to x20 say) - either by addition or by grid system or good old fashioned long multiplication.
I suppose how they get there isn't important - it's just that they do get there.