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Get Students Started with Claim, Evidence, and Reasoning (CER)

When it comes to science, we think about the natural world, investigations, and yes…experiments. It’s all about observations, seeing what happens, figuring out why, and communication.  

Science isn't just about conducting experiments and making observations, though - it's also about effective communication. Just like real-life scientists, students need to be able to express what they want to learn, predict outcomes, and summarize their discoveries. Claim-Evidence-Reasoning (CER) helps students hone their communication skills and become confidently curious young scientists. 

What is CER? 

An acronym for Claim-Evidence-Reasoning, CER is a powerful classroom tool that enables students to communicate their findings, observations, hypotheses, and ideas effectively. Here’s how it works: 

Claim (C)

The claim is a student's answer to a question or prompt. For example, a student may be asked “Why is it colder in the winter the further north you go?”  The student may answer: “Because you are getting closer to Earth’s pole.” This is the claim. 

Evidence (E)

Evidence is the “proof” the student has to justify a claim. In the beginning of a unit, this evidence could be based on background knowledge or anecdotal evidence (“All the places close to the North Pole have more snow,”, or “There is less snow the further south you are.”)  After the unit of study, the answers may incorporate more scientific data and evidence (“Because of Earth’s tilt and revolution around the Sun.”). 

The key with evidence, be it anecdotal or based in data, is that it must be relevant, valid, and reliable. 

Reasoning (R)

This is how the student connects the evidence to the claim, in other words, how they know they’re correct. 

In the beginning, this could be an anecdotal justification based on personal observations (“It doesn’t snow in the summer up north,”). After studying the topic, it can be based on the scientific knowledge they’ve gained (“The poles receive less of the Sun’s energy during the winter because of the angle of Earth’s axis, therefore there is less heat.”). It can also be a combination of the two (“It’s much colder, and snows more in the winter. This is because the poles receive less of the sun’s energy due to the angle of Earth’s axis as it revolves around the Sun. Therefore, it’s colder and you get more snow.”). 

The key is that the reasoning must show how the evidence supports the claim.

Introduce the CER Framework

Even though CER is a powerful tool for communicating ideas, evidence and justification, it’s not something many students are used to working with. You can begin by explaining CER to your students, and using examples to illustrate how to write a claim, support it with evidence, and provide reasoning to justify it, as we did above. 

Practice with Examples

Once students are familiar with the framework, give them examples of prompts so they can practice with it. For instance, you can provide a graph or chart and ask them to make a claim, support it with evidence, and provide reasoning. Alternatively, you can ask them to look at an experiment and use the CER framework to provide a conclusion. Allow students to work through examples together and encourage dialogue as well as quick feedback.

Use CER to Teach Academic Writing and Speaking

Science is not the only subject that requires critical thinking and structured arguments, especially when it comes to academic communication. By using the CER framework in science class, you are also teaching your students academic writing and speaking. Students are learning how to justify arguments, think critically, and communicate in language and tone other than casual conversation. 

These skills can benefit them in other academic subjects as well as in professional fields when they become adults. By giving them solid examples, explaining its functionality, and giving them opportunities to practice, you’re actively helping them prepare for higher education and future careers.

In Summary

The CER framework is a powerful tool that enables students to develop critical thinking, reasoning, investigative skills, and structured writing. As a science teacher, you can help your students develop and practice these essential skills by introducing them to, practicing with examples, and using structured frameworks (such as those included in Propello).


By doing so, you will empower your students to not only learn science, but also to think critically and articulate their thoughts effectively in ways that will help them succeed in other subjects and in their future professional careers.