When I first heard about CER it was in a presentation about the ELA key shifts, and my first thought was that the presenter had forgotten what she wanted to say. As she continued to talk I began to realize that this "CER" was a strategy for answering questions that she used in her classroom. The more I learned about claims, evidence, reasoning, the more I liked what I heard, but I still wasn't ready to start using it in my classroom. I was forced to make the jump though when our fifth grade teacher assigned one of my low-proficiency students an essay. She was a bit confused about the process and so I made a quick graphic organizer to help her put her notes in the correct section. This made the process much easier because we could talk about her ideas, note them in the correct section, and then later she just had to write sentences from each section in order.
My experience with CER was further enhanced when our PLC group decided to use it as the basis for our project the next term. We wanted students to use CER to answer their story problems in math. My students and I already spent a lot of time talking about why things work they way they do in math (I've been asked if Y is my favorite letter more than once), but having them actually write it out was a new experience. They tended to explain to me in words what they had done, leaving out any explanation of why they chose to add rather than subtract, for example. It took a lot of work and a lot of explaining, but they eventually became much better at the method, as well as story problems themselves. I even had one student tell her math teacher that she likes story problems the best now!
CER has been very helpful for me and my students, and I hope it will be for yours as well. Although I must admit that it's pretty funny to hear students in the hallway saying things such as, "What's your evidence for that?", or "I disagree with your reasoning.", and then realizing their heated debate is over who is the better soccer player: Messi or Pele!