Claim-Evidence-Reasoning (CER) at Mosa Mack

At Mosa Mack, we believe Claim-Evidence-Reasoning isn't just a science framework—it's an essential life skill that students need now more than ever.

Here's the reality: tweens spend over 5 hours daily on screens, and teens spend over 7 hours. During that time, they're bombarded with claims—from influencer product endorsements to viral misinformation to conspiracy theories presented as fact. Research from Stanford University found that more than 80% of middle schoolers believed an advertisement labeled as "sponsored content" was actually a news story. Less than 20% of high schoolers seriously questioned spurious claims on social media.

This is why we're so intentional about weaving CER throughout our curriculum. When students internalize the habit of asking "What's the claim? What's the evidence? Does the reasoning actually connect them?"—they carry that critical thinking lens with them everywhere, not just in science class.

We incorporate CER into lessons when it genuinely fits and enhances the learning experience. We don't cram it in just to check a box. When CER appears in a Mosa Mack lesson, it's because evaluating claims with evidence is a natural and meaningful part of that investigation.

CER also directly supports **NGSS Science and Engineering Practice #7: Engaging in Argument from Evidence**—so you're building both critical thinking skills AND meeting standards.

Claim: An assertion or statement believed to be true. A strong claim is direct, concise, and avoids opinion language like "I think" or "I believe."

Evidence: Scientific data used to support the claim. This can include quantitative data (measurements, graphs, calculations) or qualitative data (observations, diagrams, visual evidence).

Reasoning: An explanation that connects the evidence to the claim. Strong reasoning explains *why* the evidence supports (or refutes) the claim.

For classes ready for more rigor, we also support **Claim-Evidence-Scientific Principles-Reasoning (CESR)**. This adds an explicit step where students incorporate scientific concepts, laws, theories, or facts that help explain why their evidence supports the claim. This pushes students to connect their investigation to broader scientific understanding.

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View the full CER Lesson List

Below is a list of Mosa Mack lessons that incorporate Claim-Evidence-Reasoning. Some include explicit CER templates; others embed the thinking process into activities like "Construct an Explanation" or "Final Report" sections.

CER & Scientific Method Year 1: Consumer testing and claims in advertisements (Gorilla Tape, Bounty Paper Towels)

CER & Scientific Method Year 2: Refresher lesson on consumer testing and claims in advertisements (Reynolds Wrap)

Biodiversity Lab Extension: Students evaluate a claim that "ecosystem disruptions are no big deal because an event in one part of the ecosystem won't impact biodiversity in a region."

Genetic Variation Lab Extension: Students crack the case—which family does baby Alicia belong to? They use Punnett Square evidence to prove their claim with reasoning.

Genetics vs. Environment Lab: Students make a claim about whether genetics or environment has more impact on organism growth, then support it with evidence and reasoning.

Atoms & Molecules Lab Extension: Students determine whether Lucas or Maggie has the correct answer, providing evidence and reasoning. *(CER template not explicitly provided but the thinking process is embedded.)*

States of Matter Lab: Students figure out how to transport blood to patients under heat and pressure. They evaluate claims from three doctors and provide evidence and reasoning for why one is correct.

Thermal Energy Lab: Students test two claims made by an infomercial salesman about how thermal energy moves through his gloves.

Earth Spheres Solve: The mystery investigates a claim made by "Petro Proud Petroleum" that what happens in one sphere only impacts that sphere.

Matter and Its Interactions: Students make a claim about what type of mystery matter they have and use evidence to support it.

Photosynthesis Lesson 1 Phenomenon: Students determine if the defendant is guilty of killing a tree based on evidence. *(The "Construct an Explanation" section models CER thinking and can easily be paired with a CER template.)*

The Nature of Science Lab: In the Final Report, students make a claim about who stole the popcorn and provide evidence and reasoning. *(CER template not explicitly provided but the process is built in.)*

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CER Lesson List — A sortable list of all lessons with CER components

Many of these lessons include downloadable CER or CESR templates, posters, and graphic organizers. Check the lesson materials for available resources, or reach out to our team if you'd like support implementing CER in your classroom.