Once you've done the numbers 1 to 12 song, and practiced them in a few themes such as How many?, How old are you? or What time is it?, you can use this song to easily teach the numbers from 13 to 20. My personal
favourite is to do it straight after the How much? song, where you can do the bargaining game again, this time with the prices being between 13 and 20 - it gets the
kids thinking!
On CD8 there's also a version from 13 to 32, and to be honest I usually prefer
that one from the beginning, but see how you go with your students.
On the CD there are also two computer games, one is a straight quiz of numbers 13
to 20, but the other is a listening quiz to distinguish between 13 and
30, 14 and 40 and so on. This is often something that needs to be practiced.