There is a ghost in the English room

Well, that's what my 6th grade girls told me Monday morning. They were at school on Saturday and walked by my class and knocked on the door even though they know I'm not there usually. But they claim to have heard someone in English tell them to come in... but the door was locked. So they walked around to the other door and broke in to my room. Where they heard someone talking in English but no one was there.
So I had several different groups of students tell me this on Monday. Then late Wednesday I got a text from one of them telling me that I had to be careful cause there was a ghost in my room.
I was telling this to the part time co teacher I have two days a week and she was surprised.. and then started to joke around like she was talking to the ghost in English.

What makes this even more interesting are a couple of things. Koreans are really superstitious about spirits, etc. So that a bunch of kids say there is a ghost in my room folks take it a bit serious. Though they worry that it's a "foreign ghost" if it's speaking English. I said no it was Korean, just had paid attention in my classes. Which got a few laughs.. but I'm sure the next Saturday there is classes they will be keeping an eye on my classroom.