The new 172 models (R and S) do not have the 40° flap setting, which was the one that got students into difficulties. At 30° flap, the aircraft is quite controllable at full power on most days. Bear in mind the 172 now has a 180hp engine too.
Anyhow, the manual dictates retracting one notch as soon as possible on a go around, similar to many of the airline procedures according to comments above.
The issue of "how to teach students bound for bigger aircraft" is quite interesting, but probably should occur on the Instructors' forum. I'll reply to any post there...
cheers to all,. .O8