Claim Evidence Reasoning (CER): Examples, Sentence Starters, and a Rubric

Claim evidence reasoning (CER) is a three-part structure for writing an explanation or an argument: a claim that answers a question, evidence that supports the claim, and reasoning that explains why the evidence proves it. Science teachers use it for lab conclusions, ELA teachers for literary analysis, and social studies teachers for document-based answers. The part students skip is reasoning, and it's the part that shows they understand.

This guide defines each part, walks through one full example, and then gives CER examples for science, ELA, social studies, and math. It ends with sentence starters for each part, a rubric with level descriptions, the mistakes students make most often, and how CER compares with RACE and ACE.

What Claim, Evidence, and Reasoning Mean

Each part answers one question.

• Claim: What is your answer? A one-sentence statement that answers the question being investigated. In science it's a conclusion about what happened. In ELA it's an interpretation of a text.
• Evidence: How do you know? Specific data, observations, quotes, or facts that support the claim. Evidence has to be relevant to the claim and specific enough to check: "Our data shows it" isn't evidence; "The cube dissolved in 55 seconds at 60°C" is.
• Reasoning: Why does that evidence prove your claim? The bridge between the evidence and the claim. In science, reasoning applies a scientific principle. In ELA and social studies, it explains what the evidence shows and why it matters.

The framework was popularized for science classrooms by Katherine McNeill and Joseph Krajcik, whose research on supporting students' scientific explanations underlies many of the CER rubrics teachers use today. It fits the Next Generation Science Standards practice of engaging in argument from evidence, and the Common Core writing standards, which ask students to support claims with clear reasons and relevant evidence.

A Claim Evidence Reasoning Example, Step by Step

Here's one CER built from a common middle school lab.

Question: Does the temperature of water affect how fast sugar dissolves?

Data: Students dropped one sugar cube into 100 mL of still water at three temperatures and timed how long it took to disappear, three trials each. Average times: 290 seconds at 10°C, 160 seconds at 25°C, and 55 seconds at 60°C.

Claim: "Sugar dissolves faster in warmer water."

The claim answers the question directly. It doesn't hedge ("temperature might matter") or restate the question ("temperature affects dissolving").

Evidence: "In our trials, a sugar cube took an average of 290 seconds to dissolve in 10°C water, 160 seconds in 25°C water, and 55 seconds in 60°C water. Each increase in temperature shortened the dissolving time."

The evidence uses the actual numbers and points out the pattern that matters. It describes all three conditions, not just the most dramatic one.

Reasoning: "Temperature is a measure of how fast particles are moving. In warmer water, water particles move faster and collide with the sugar cube more often and with more energy, which pulls sugar molecules away from the cube sooner. That's why the cube dissolved more than five times faster at 60°C than at 10°C."

The reasoning names the science principle (particle motion) and connects it to this data. Without it, the student has shown that warm water works faster but not why, and the "why" is what the lab was designed to teach.

Compare a weak version of the same response: "Sugar dissolves faster in hot water because it is hotter. Our data proves this." The claim is fine. The evidence is missing (no numbers), and the reasoning repeats the claim. It would score well on the claim and poorly on the other two parts.

CER Examples for Science, ELA, Social Studies, and Math

CER works anywhere students have to support an answer with evidence. The parts stay the same; what counts as evidence and reasoning changes by subject.

Science CER example

Question: Which material keeps a drink cold longest: aluminum foil, a wool sock, or a plastic bag?

• Claim: "The wool sock kept the drink cold longest."
• Evidence: "After 60 minutes, the water wrapped in wool rose from 5°C to 11°C, the water in plastic rose to 15°C, and the water in foil rose to 17°C."
• Reasoning: "Heat moves from warmer areas to cooler ones. Wool traps pockets of air, and air is a poor conductor of heat, so less heat from the room reached the cold water. Aluminum is a good conductor, so heat moved through it fastest."

ELA CER example

Question: Is the narrator of Edgar Allan Poe's "The Tell-Tale Heart" sane?

• Claim: "The narrator's insistence that he is sane is the clearest sign that he isn't."
• Evidence: "He opens by asking 'why will you say that I am mad?' and then offers his careful planning as proof, boasting about 'with what caution—with what foresight' he crept into the old man's room every night for a week. He also admits there was no motive: 'Object there was none. Passion there was none.'"
• Reasoning: "A sane person wouldn't use the patience of a murder plan as proof of a healthy mind. The narrator confuses being calm and precise with being reasonable, and his admission that he had no motive removes the only explanation that could make his actions make sense. Poe lets the narrator's own argument convict him."

In ELA, the reasoning is analysis: it explains what the quotes reveal. A strong ELA claim works the same way as a strong thesis statement. Our guide on how to write a thesis statement covers making a claim specific and arguable.

Social studies CER example

Question: Did the Erie Canal help New York City grow?

• Claim: "The Erie Canal helped New York City grow by making it the cheapest outlet for goods moving between the Midwest and the Atlantic."
• Evidence: "After the canal opened in 1825, the cost of shipping a ton of freight from Buffalo to New York City fell from about $100 to about $10. The city's population rose from about 124,000 in 1820 to about 313,000 in 1840."
• Reasoning: "When shipping costs fall by about 90%, farmers and merchants send their goods along the cheapest route. Because that route ended in New York City, the trade, the jobs that handled it, and the people who took those jobs all came to the city."

This is the structure of a strong DBQ body paragraph or AP short-answer response: a claim, document evidence, and an explanation of how the evidence supports the claim.

Math CER example

Question: Is the sum of two odd numbers always even?

• Claim: "Yes, the sum of any two odd numbers is even."
• Evidence: "3 + 5 = 8, 7 + 11 = 18, and 21 + 9 = 30. Every example we tried gave an even number."
• Reasoning: "Examples alone don't prove it's always true, so here's why. Every odd number is one more than an even number, so it can be written as 2a + 1. Two odd numbers add up to (2a + 1) + (2b + 1) = 2a + 2b + 2 = 2(a + b + 1), which is 2 times a whole number. That's the definition of an even number."

The math example makes the role of reasoning especially clear: evidence shows a pattern, and reasoning shows why the pattern has to hold.

CER Sentence Starters for Each Part

Sentence frames help students who know the content but freeze at the blank page. Post them on an anchor chart and remove them as students get comfortable.

Claim sentence starters

• "Based on the data, I claim that..."
• "The answer to the question is..."
• "In [text], the author shows that..."
• "[Event or factor] caused / led to..."

Evidence sentence starters

• "In our investigation, we observed that..."
• "The data shows that [specific number or pattern]..."
• "In paragraph [number], the author writes, '...'"
• "According to [document or source],..."
• "For example, when [condition], [result]."

Reasoning sentence starters

• "This evidence supports my claim because..."
• "This shows that... because..."
• "The scientific principle that explains this is..."
• "This matters because..."
• "If [claim] were not true, we would expect..., but instead..."

Rebuttal sentence starters (for CER with counterclaims)

• "Some might argue that... However, the evidence shows..."
• "Although [opposing evidence], this doesn't change my claim because..."

The phrases that introduce and explain evidence are a subset of essay transitions. Our list of transition words for essays has more, sorted by purpose.

How to Teach Claim Evidence Reasoning

CER improves with explicit modeling and repeated practice across the year. A sequence that works in most grades:

1. Start with a mystery that isn't academic. "Who took the cookies from the break room?" with a few clues. Students make a claim, cite the clues, and explain how each clue points to the culprit. Edutopia's Eric Brunsell recommends starting with non-science mysteries like this so students learn the structure before the content gets hard.
2. Model one with your own think-aloud. Write a CER in front of the class, saying out loud how you chose the claim, which evidence you kept, and how you wrote the reasoning.
3. Color-code. Have students highlight their claim, evidence, and reasoning in three colors. A response with almost no reasoning color is easy to spot, for you and for them.
4. Critique examples before writing. Give students three responses to the same question, weak to strong, and have them score each with the rubric. Students who can see why a response is weak write stronger ones.
5. Give data, then let them collect it. Early on, provide the data table so students focus on the writing. Later, they use data from their own investigation.
6. Fade the frames. Keep sentence starters available, then move them to a reference sheet, then remove them.

A Claim Evidence Reasoning Rubric

This rubric scores each part from 0 to 3, for a total of 9. It's simple enough to use on every lab conclusion and detailed enough to tell students what to fix.

Claim

• 3: Accurate, complete, and directly answers the question.
• 2: Accurate but incomplete or vague.
• 1: Inaccurate, or doesn't answer the question asked.
• 0: No claim.

Evidence

• 3: Relevant and sufficient. Uses specific data, observations, or quotes, and includes all the evidence needed to support the claim.
• 2: Relevant but not enough of it, or not specific (for example, "the hot water was faster" without numbers).
• 1: Evidence doesn't support the claim, or is opinion rather than evidence.
• 0: No evidence.

Reasoning

• 3: Explains how each piece of evidence supports the claim, using the relevant scientific principle or a clear explanation of what the evidence shows.
• 2: Connects some evidence to the claim, or names a principle without applying it to this evidence.
• 1: Restates the evidence or the claim without explaining the connection.
• 0: No reasoning.

For a rebuttal row, add: 3: names a plausible counterclaim and explains with evidence why it doesn't hold; 0: no counterclaim. Adjust the wording for younger students, and add a row for scientific vocabulary or conventions if you grade those.

To turn this into a printable rubric with your own wording, paste it into the free rubric generator and ask for a lab report or CER rubric at your grade level.

Common CER Mistakes

The claim restates the question. "Temperature affects how fast sugar dissolves" doesn't say how. A claim should take a position the evidence could prove wrong.

The evidence is vague. "The data shows it" or "the hot water was faster" leaves out what makes evidence convincing: the numbers. Ask students to include at least one specific measurement or quote.

The reasoning repeats the evidence. "This supports my claim because the time went down as the temperature went up" restates the evidence in different words. Reasoning has to answer why.

The claim says "proves." One lab with three trials supports a claim; it rarely proves it. Students should learn to write "the data supports" and save "proves" for math.

Evidence that contradicts the claim is ignored. If one trial didn't fit the pattern, the strongest responses mention it and explain it (a measuring error, an unstirred cube) instead of leaving it out.

Too many claims. A CER answers one question. If students make three claims, the evidence and reasoning get spread too thin to support any of them.

CER vs. RACE, ACE, and PEEL

Several writing frameworks share CER's DNA. Which one a school uses usually depends on the subject.

• CER (Claim, Evidence, Reasoning): Common in science and increasingly in ELA and social studies. Its strength is the explicit reasoning step.
• CERR (Claim, Evidence, Reasoning, Rebuttal): CER plus a counterclaim. Good preparation for argumentative essays.
• RACE (Restate, Answer, Cite, Explain): Common in elementary and middle school ELA for short constructed responses. "Cite" is evidence; "Explain" is reasoning.
• ACE (Answer, Cite, Explain): RACE without the restating step.
• PEEL (Point, Evidence, Explain, Link): Common for body paragraphs in essays. "Link" ties the paragraph back to the thesis.

They all teach the same habit: make a claim, back it up, and explain the connection. If students learn RACE in ELA and CER in science, point out that "Explain" and "Reasoning" are the same move.

Grading CER Responses Faster

The reasoning row is the slowest to grade, because it needs a comment, not just a score. A few habits help:

• Grade one row across the whole class set before moving to the next. Comparing every student's reasoning side by side makes the scores more consistent.
• Keep a bank of comments for the most common reasoning gaps ("Your reasoning restates the evidence. What principle explains it?").
• Quote the student's own sentence in the comment so the fix is concrete.

If you grade CER with GradeWithAI, it scores each rubric row and writes a comment that quotes the student's claim, evidence, or reasoning, and you edit any score before students see it. It reads typed responses and photos of handwritten lab conclusions, and works for short answers through the short answer grader or any other assignment through the assignment grader.

Frequently Asked Questions

What is claim evidence reasoning?

Claim evidence reasoning (CER) is a framework for writing scientific explanations and arguments. Students make a claim that answers a question, support it with evidence, and use reasoning to explain why the evidence supports the claim.

What is an example of claim evidence reasoning?

Claim: "Sugar dissolves faster in warmer water." Evidence: "A sugar cube dissolved in an average of 290 seconds at 10°C and 55 seconds at 60°C." Reasoning: "Water particles move faster at higher temperatures, so they hit the sugar more often and pull it apart sooner."

What is the difference between evidence and reasoning?

Evidence is what you observed or found: the data, the quote, the fact. Reasoning explains why that evidence supports your claim, usually by applying a principle or explaining what the evidence shows.

What grade level is CER for?

CER is used from about third grade through high school. Younger students use simple frames and teacher-provided evidence. High school students write full explanations with multiple pieces of evidence, scientific principles, and rebuttals.

Is CER only for science?

No. CER started in science but works in ELA (evidence from a text), social studies (evidence from documents), and math (evidence from examples, reasoning from properties).

How long should a CER response be?

A short CER can be three sentences, one per part. A lab conclusion or document-based answer is usually a paragraph. The reasoning is often the longest part.

What does CERR stand for?

CERR is claim, evidence, reasoning, rebuttal. The rebuttal acknowledges a counterclaim or contradicting evidence and explains why the claim still holds.

How do you grade CER?

Use a rubric that scores claim, evidence, and reasoning separately, such as the 0 to 3 rubric above. Scoring each part separately shows students exactly which part to improve.

Sources

• Eric Brunsell, Designing Science Inquiry: Claim + Evidence + Reasoning = Explanation, Edutopia (2012)
• Katherine L. McNeill and Joseph Krajcik, Supporting Grade 5–8 Students in Constructing Explanations in Science: The Claim, Evidence, and Reasoning Framework for Talk and Writing, Pearson (2012)
• NGSS Lead States, Appendix F: Science and Engineering Practices in the NGSS (2013)
• National Research Council, A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (2012)
• Common Core State Standards Initiative, Writing Standards, Grade 8
• MIT BLOSSOMS, Resource Sheet: Claim-Evidence-Reasoning