[adrianN]

There is also a whole different language used to talk to toddlers and small children that native speakers know but very few adult learners ever pick up. And slang used among teenagers and young adults that often times not even their parents understand fully.

[dspillett]

The problem with adding slang to any organised education program is two-fold: some of it changes much more quickly than you course materials can, and much of it is quite localised.