What CER Actually Looks Like When You Try to Use It
Claim Evidence Reasoning is a structured way of building arguments, mostly in science classes but also in history and social studies. You make a claim, you back it up with data, and then you explain why that data supports the claim. The framework itself is straightforward. Getting students or colleagues to actually do it well is another thing entirely. The claim is your answer. It should be a clear statement that directly addresses the question or problem. "The plant grew faster with fertilizer" works. "Plants like stuff" does not work. Keep it specific and testable. Evidence is the data you collected or observed. This is where most people mess up. Evidence has to come from a reliable source, and it has to be relevant. A chart showing growth rates over two weeks is evidence. A textbook definition of photosynthesis is not evidence unless you also tie it to your specific data.
Reasoning connects the two. It explains why the evidence supports the claim. This is usually the weakest part. People tend to just restate the evidence in different words instead of actually explaining the logical link. Good reasoning references scientific principles or established methods. "Chlorophyll captures light energy, which the fertilizer helped the plant use more efficiently, resulting in faster growth" is better than just saying "the fertilizer made it grow bigger." I spent years watching people fail at this. The most common issue is that evidence and reasoning get mixed up or left out entirely. You will see claims with no evidence, or evidence dumps with no reasoning. That is not CER. That is just an opinion with some numbers attached. Here is a practical example from a lab report I reviewed last month. The claim was that temperature affects enzyme activity. The evidence included a graph of reaction rates at different temperatures. The reasoning explained denaturation and kinetic energy. Three sentences each section. Clear, direct, and defensible. That is the standard.
How to Actually Teach or Learn CER
Start with the claim. Before anyone touches data, they need to know what question they are answering. Write the question on the board. Have every person or group write their claim before doing any. This forces them to think about what they are trying to prove before they collect anything. Then move to evidence. Students often grab the first number they see. Train them to ask: does this number actually relate to the claim? If the claim is about temperature and enzyme activity, a measurement of pH is irrelevant evidence even if it came from the same experiment. Filter out noise early. Reasoning is the hardest part. Give people sentence starters. "This evidence supports the claim because..." "According to the principle of..." These force the connection to exist on the page instead of being assumed. It feels mechanical at first. It works.
Get the Full Details
One edge case I ran into that surprised me: sometimes the evidence contradicts the claim. A student might have designed a bad experiment or collected faulty data, but they wrote a claim anyway. In those cases, the claim should reflect what the data actually shows, not what the student hoped it would show. I had one student who got completely flat results in her enzyme trial but still wrote a claim about optimal temperature. We went back and revised the claim to match the data. The reasoning then explained why the data might be unreliable rather than supporting a false conclusion. That is a legitimate CER structure that most rubrics do not explicitly cover but is important for actual scientific thinking.
Common Pitfalls and How to Avoid Them
Pitfall number one: the evidence is just a restatement of the claim. "The plant grew more with fertilizer because the fertilizer helped it grow." That is circular. Evidence must be independent data, not a paraphrase. Pitfall number two: reasoning without citing a principle. "The data shows X, therefore Y" is incomplete. You need to explain why X leads to Y using an established concept. Without that, you have an assertion, not an argument. Pitfall number three: using anecdotal evidence. "My friend said it worked" is not evidence in a CER context. Data points, observations, measurements, and citations from credible sources are what count.
Another counterintuitive thing: CER works best when the claim is narrow. Broad claims like "climate change is bad" are nearly impossible to support with specific evidence in a single paragraph. Narrow claims like "increased CO2 concentration accelerated algae growth in the sample" are much easier to build and evaluate. There is also a limitation worth mentioning. CER breaks down when dealing with complex, multidisciplinary questions. Questions about policy, ethics, or systems with too many variables do not fit neatly into three boxes. For those situations, Toulmin's model of argument or a simple pros-and-cons framework may be more appropriate. CER is a training tool and a writing scaffold, not a universal argument structure.
Where to Find CER Templates and Rubrics
There are free CER templates available through educational resource sites. Many school districts publish their own versions online. Search for "Claim Evidence Reasoning template PDF" or "CER rubric elementary" depending on your level. The key is to pick a template that separates evidence and reasoning clearly. Some templates combine them into one section, which defeats the purpose. If you want something ready to use, the SMART Institute at Arizona State University has CER materials that are openly available. Their template format is clean and the rubric distinguishes between weak and strong reasoning clearly. I have used it in my own classroom settings for over a decade. It works. Another option is to create your own template based on your specific subject. Science teachers might want a template that includes a section for hypothesis. History teachers might add a source credibility check. The structure matters less than the habit of making the three parts explicit.
The bottom line is that Claim Evidence Reasoning Practice is not about following a rigid formula. It is about learning to distinguish between what you think, what you observed, and why the observation supports the thought. Get good at that distinction and you get good at almost any form of analytical writing. I still see people skip the reasoning step even now. It happens. Keep pushing for it. The quality of the argument improves every time someone writes the connection out loud instead of assuming it is obvious.
