It looks like I not only teach my students English, but can also (in one case!) help them with their Korean grammar.
I have a couple of intermediate classes that are currently learning about measure words (numeral classifiers), and to help them on the subject I broke up the grammar lesson into a couple of parts. To start with, I wrote the word 'Noun' at the top of the board and made sure everyone was familiar with the concept. I usually include the Korean translation (명사) under the English for lower-level classes and then drop it once I know students understand the English meaning.* Under that I drew an arrow to the left of the board and wrote the word 'Countable' next to it. I had students list off countable nouns - tiger, orange, teacher, computer game - and then drew an arrow to the right of the board and wrote the word 'Uncountable'.
When I asked students to tell me some uncountable nouns they gave me another list - water, juice, soju, milk, paper - but looked confused when I asked them about what 'helping words' go with the uncountable nouns. Great, at that point I knew where to really get involved with the lesson. Unlike in English, the Korean language constantly associates measure words with objects and events - similar to Chinese and Japanese - so to prime my students I asked them about Korean measure words.
To start with I wrote 개 (gae; from the Chinese 個) on the board, the counting word for general objects and one that can be used when one isn't sure what other term to use. From there I asked students for other examples. One student said 마리 (mari) for animals, a boy chimed in with 병 (byeong; Chinese 甁) for bottles, and one added 명 (myeong; Chinese 名). For fun I then asked if they could tell me the Korean measure word for bananas. It was supposed to be an easy question, but I didn't take into account that my students are only in third and fourth grade and might not have much experience with the correct term -- 송이 (song-i). Is this covered in elementary school or something that students are expected to have picked up on their own?
The first response I got was 마리. (The measure word for animals, remember.) The second was 명, which might work for this guy (note: animated .gif) but is usually not the case. The third guess ventured into new territory with 톨 (tol, used for uncooked grains of rice and stones) the proposed answer. Maybe it's just me, but I found the first response amusing if a bit unexpected. I asked the same question - with a condensed lead-up - to a pair of other classes and they were also at a loss. 송이 is used for bunches of things, including bananas, grapes, and picked flowers (i.e., in a bouquet) and was one of our tested vocabulary terms at my Korean-language hagwon. Hmm. Looks like I might be better off leaving out that part of the lesson in future classes.
I pointed all this out to my co-teacher after class and she was also surprised. However, she also mentioned that one of the girls in our class often mixes up the topic marker (는/은) and object marker (를/을) in her Korean, which was interesting to hear. Given how often these markers can be (are?) dropped from casual speech I wonder if this causes problems for any other younger students.
Edit: Oh yes, following the '송이 incident' we did return to the original topic and I explained the use of English measure words such as piece, cup, loaf, slice, and bar. You know, for anyone who might have been wondering about that.
* Yes, this is technically cheating, but there's nothing like having a lesson get derailed by student questions. A noun is "a person, place, or thing" but sometimes students ask what "thing" means. Hmm, a thing is an object and often one that you can touch. Ah, and what do the words object and touch mean? Well ...