I believe there are two main (classroom) reasons why students lose focus and start being disruptive in a CI class. 1)The input you're (read: I am) giving is boring. And 2) the input that you're giving is incomprehensible. This is my third year teaching, and third year using TCI/TPRS in my classroom. Every year, every semester I have gotten to a point where I lost students. I start getting incomprehensible because I'm over-estimating what is comprehensible to students. Students were getting frustrated and restless, and I was getting frustrated and restless. It was because instead of going i+1 I was going i+1000. That wasn't doing any good for anyone.
At the beginning of second semester I did not take the time to review the Super Seven . This was such a big mistake. These are words that I use every day, but I had not taken the time to establish the meaning for the students I didn't have last semester.
So I started over. Last week I spent a couple days TPR-ing the super seven. Students were familiar with these but they were nowhere near being able to recognize them without a lot of support (which is fine, but I knew I could be doing more to help them). I LOVE using TPR from time to time. During TPR a student said "These are too many words and I'm not going to remember all of these gestures" And then it was the end of the week and I did some review of the TPR and they sure did remember all of the gestures. The human brain is amazing, guys. Connecting these words to gestures and connecting the gestures to meaning is so powerful.
After doing this TPR we moved into a story. It was the most successful story-asking days that I've had this year. It was the first time I tried doing parallel characters, and it was great. So many reps of the target structures, so much more comprehension, and so much more production!
It was a great week, and if you feel like you've lost your students somewhere along the way this year, just start over. You'll be happy you did, and your students will be happy you did.