"Get a brew on" is rarely used in the USA as far as I know. On the other hand, the slang that you find "abominable" in your own words is quite common and accepted in English speaking countries not called England. A bit biased there on your part in my opinion.

Well "kick ass" and stuff was originally used in England-asses are known as stubborn animals who need kicking, if you want to get it moving- so, in its true meaning it's perfectly okay to use and to teach. Anyway, I know many educated Americans, who are more likely to teach the students not to ingratiate yourself as opposed to using 'brown nose'

Anyway, I haven't noticed any faults with your English, Dragonised, so I imagine that you are a good teacher.

I didn't know I was speaking to the former Minister of Education, or one of the original Writers of the Oxford English Dictionary. Pheeeew I "imagine" I would be flattered if this was the case.

It is interesting to teach slang, but only if the students are very very good at what they know and can understand you fully. I think for me teaching something like this will only lead to more and more words I have to explain to my students until the whole point of teaching slang which is to induce a fun atmosphere gets lost in translation. We can all save the slang for good times in the evening when we get together with other foreign teachers. If you do choose to work in the ESL field you will get a chance to learn how fun the English language really is.