"Sorry, I don't English."

I walk home from school everyday around 4pm. This means that the only other people who are out on the streets are middle school and elementary students, and they all love to wave and say "hiiiiii" to me. I walk with my earphones on, but can usually spot them and lift my hand to wave fast enough that it's not considered rude. Sometimes I don't notice right away, but eventually realize that there is a small group of 5 year olds across the street in a huddle shouting "hi" at me. To this I always respond with a loud "hello" over the traffic that separates us, causing them to giggle in unison. All of this has become part of my daily routine; in fact, it would feel strange if I walked home without so much as a glance from the kids in the street. Today I was leaving my high school and I saw a group of about 7 middle school girls from the same school that my younger host sister, Sue Jeon, goes to. These girls were about 5 feet in front of me, and took turns twisting their necks in my directions and smiling with a small wave and a "hiiiii". I of course, did my normal wave and "hi" in response, but I decided to ask them if they knew my sister Sue Jeon, as they looked about her age. In Korea you can't just ask someone if they know Go Sue Jeon, because that would be like asking if they know John Smith times five. I noticed the other day when I was taking roll with my students, rather than two or three Smith, Anderson, Martinez or Hernandez last names in a classroom; there are like 10 Kims and 7 Gos, etc. This means that there are really only 5 last names that the whole classroom splits and some of the more popular names, like Kim Soyeon, have one per class at least. Instead of asking these girls if they knew Go Sue John, I asked them what class they were in, because my sister is in the second grade. I thought I could narrow it down from there; however, when I asked slowly and clearly: "What grade are you in?" The girls' faces showed nothing more than blank stares, if anything they just looked puzzled. From my point of view, I don't understand why it's puzzling that when you wave, stare, and yell "hi" to someone repeatedly in the street they strike up a conversation with you. I asked again and the girls stopped, still puzzled, but smiling. Finally one girl held up her hand (as if to say "stop") smiled, scrunched up her nose, and in a sweet voice said: "Sorry, I don't English." To this I responded with sincere comprehension: "Oh, you don't English."