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I know this is an old thread, but just in case someone else (like me!) is new and reading everything, I'll add my two cents.

I read a really good article here:
http://www.apa.or...glish.html
about English getting in the way of kids learning math, as compared with their asian counterparts. This, according to the article, is based on the words we use for number values. In Western cultures, we get to 10 and then go into the teens (confusing), and then switch to 20's, 30's, 50's, whose names don't even match the initial number, and then the 40's, 60's, 70's, 80's and 90's whose fact that the names match the initial number is different from the others. (even typing that out was confusing).

Teeco and I express our numbers like this:

1-10, as normal.
11-19 as "one ten one, one ten two, one ten three...etc."
20-19 as "two ten, two ten one, two ten two, two ten three...etc."
30-39 as "three ten, three ten one, ...etc."

So the number of tens are expressed followed by the ones. This makes writing the number easier, as well as if we are trying to mentally add them.

HTH!