CER stands for Claim, Evidence, Reasoning, and it is a framework used in science classes to help students think critically and support their ideas. It is a three-step process that requires students to make a statement (claim), provide evidence to support their statement, and explain the logic behind their statement (reasoning) . CER is used to create a well-structured argument that answers a question about a scientific phenomenon. Students use this framework to write an argument when there is more than one possible claim or answer to a question.

The CER format to writing explanations is not a trivial thing for students, and teachers need to explicitly introduce and model it for them. Teachers can use concrete (non-science) situations, like mysteries, images, artwork, etc., to introduce CER to their students. Teachers can also create an anchor chart, use a rubric with students to critique examples, provide examples from science or scientists, and create CER worksheets with data provided by the teacher.

CER is a useful tool for developing students analytical thinking and argumentative writing skills. It can be used in the lab setting to help students create clear, written arguments. By using the CER tool, students are able to explain their scientific understanding and develop their critical thinking skills.