I was sitting here thinking about how I could use QR codes a bit more effectively in class while giving them breaks here and there and not have to repeat myself over and over. Right now, I use them for warm-ups and sometimes for sending them to web pages. It just struck me that I could put QR codes with instructions for the next step in the class work, or what paper they need to collect from me. Students, even high school students, need to get up once in a while and move to help them so they don't get restless. Since I have my students sit and work in groups, I can have one person from each group go up to the QR code, read it and take back the information to their seat mates or follow the directions and collect worksheets from me. Then for the next activity, have another student get up so there is not a mass clog at the QR code location.
I can also use the QR codes as a ending class activity so they place the answer inside a QR code with their QR code maker app and I scan it as they clean up and put the iPads away. It is a simple for me to scan their answers and check them. I am planning to start sending homework home soon with a QR code embedded on the sheet with the answers. They will still have to work the problems so I can see the process but they will know what the answer is supposed to be. If you know where you are heading, it makes it easier to do the math problem.
I know there are lots of places out there that discuss using the QR codes in the classroom but each class is different and your choice of how you use the codes will vary.