The On Going Struggle With a Class that Won't Talk

I mentioned in a previous post about the struggles of teaching and that one of the classes that I teach doesn't like to talk very much. Well I still don't know what to do with this class. The class used to have 6 students, but has gone down to 5, as one of the students moved up a level.

Let me give you some background on these students. These students are in middle school and have been studying English for a while and are at a low intermediate level (meaning they can speak and understand English enough, but still need to study lots). I have been teaching 3 of them since I arrived at the school and the other 2 have just started in the last 2 months. When I first came to the class I noticed that it was extremely quiet and I had a hard time getting them to answer the simplest questions. At first I just thought that it was the text book and that it was too boring for them. However, we finished the text and I got a text that I thought would be good for them with very interesting topics. Well nothing has changed, if not things have got worse. It's not that they are not understanding the text, because I asked the head teacher about it and she said that they have studied it previously.
So I'm kind of stuck with this class. I ask them questions, very easy ones, and the usual answers I get are 'I don't know,' 'Sleeping,' and 'Let's play a game.' Every class with them is like torture for me because I end up standing there staring at them hoping for them to answer my simple questions. It's very awkward. They always just want to play a game or do nothing.
I asked the head teacher what I should do with them and she doesn't know either. She says that they should practice speaking in class because with me they can get real conversation and good practice, but they don't want to do any of that.
I actually just found out yesterday that one of the students, one of the newer ones, enjoys my classes. I thought this was impossible because she is one of the most quiet students in class. I found out that she is scared to talk in class because she doesn't want to be wrong, but when she does say something she is surprised that I understand her. This made me so happy, because at least she is understanding and wants to talk, she is just shy. I found this out through her mother, who came to talk about her daughter to the head teacher.
So this gives me a little hope for the class, but I still don't know what to do and how to go about making them speak. It's so hard.