I'm sad to say that after a few months I stopped teaching him. Partly because I don't know enough to really teach him, and partly because of other selfish factors like me being unmotivated to continue. I was reminded today of how much he loves it, though. It reminded me that I really want him to learn this, especially since he is so interested.
I came home during my break today to find that Latu has added to Mason's knowledge. She has taught him a very important sentence. I was so impressed that I hurried and recorded it. I almost cried the first time I watched him do this. The sentence is: "I have cancer, so I go to the doctor to fix it." He has it memorized, but was a little shy to do it by himself for the camera (who would have thought?), so Latu helped him out.