Claim-Evidence-Reasoning Science Starters for Middle School
A short data set, a careful claim, and a better reason than “because that is what happened.”
A student can fill three boxes labeled claim, evidence, and reasoning and still miss the point of the explanation. The claim may be an opinion, the evidence may be a copied sentence, and the reasoning may repeat both.
For me, the useful question is simple: does the student explain how the evidence supports the claim? These claim-evidence-reasoning science starters give teachers a small, focused way to practice that connection before asking for a full lab explanation.
“I can use relevant data and a science idea to support a claim, so someone else can follow and evaluate my explanation.”
- My claim answers the question.
- My evidence includes relevant measurements and units.
- My reasoning explains the connection and respects the limits of the data.
Give students something to reason from
Start with a small data set rather than a broad question such as “Is more light better for plants?” That question needs conditions, measurements, and a careful definition of “better.” A narrower question makes the task more manageable.
Question to display: In this model investigation, which group of seedlings had more height growth over seven days? What do the data support, and what do they leave uncertain?
Important: The numbers below are fictional teaching data, not results from my classroom or a published experiment. Imagine six similar seedlings of the same species assigned to two groups, with water, soil, container size, temperature, and light intensity kept consistent. Only daily light duration differs.
| Daily light | Seedling 1 | Seedling 2 | Seedling 3 | Mean increase |
|---|---|---|---|---|
| 6 hours | 2.0 cm | 2.2 cm | 1.8 cm | 2.0 cm |
| 10 hours | 3.0 cm | 3.2 cm | 2.8 cm | 3.0 cm |
Model the difference between evidence and reasoning
Answer the question
In this data set, seedlings receiving 10 hours of light had more height growth over seven days.
Name the measurements
The 10-hour group grew an average of 3.0 cm, compared with 2.0 cm for the 6-hour group. Every seedling in the 10-hour group grew more than any seedling in the 6-hour group.
Explain the connection
The comparison supports the claim about these groups because the measured height increases are consistently larger in the 10-hour group. Light supplies energy for photosynthesis, which produces sugars plants can use to build material. That science idea offers a possible explanation, but height alone does not establish how much photosynthesis occurred.
Keep the limitation in the model response. Six seedlings, one species, and seven days do not justify a claim about every plant. More light is not automatically better under all conditions, and height is not a complete measure of plant growth or health.
Run the starter in about eight minutes
- Notice for one minute. Students identify the quantities, units, and comparison.
- Draft for three minutes. Students write a claim, select evidence, and connect it to a science idea they have studied.
- Discuss for two minutes. Partners ask, “Which number supports that?” and “How does your science idea connect?”
- Revise for two minutes. Each student improves one sentence and names one limitation.
The timing is a suggested routine, not a requirement. If students need support interpreting the table, spend the time there rather than rushing into a paragraph.
Use feedback that points to a specific revision
| If a student writes… | Try this response |
|---|---|
| “The plants liked more light.” | “Replace ‘liked’ with the measured outcome. What changed, and by how much?” |
| “The evidence is that they grew more.” | “Add both group means and the unit. Help your reader check the comparison.” |
| “My reasoning is that 3 is bigger than 2.” | “That compares the numbers. Now connect the pattern to a relevant science idea and state what is still uncertain.” |
| “All plants need exactly 10 hours.” | “What did this investigation actually test? Narrow the claim to these groups and this measurement.” |
For language support, let students explain orally before writing. Keep claim, evidence, reasoning, variable, and limitation visible. Offer “The data show ___ compared with ___. This supports ___ because ___. We cannot yet conclude ___.” Then remove parts of the frame as students become more independent.
Keep the routine; change the evidence
For the next starter, use a short graph from a current investigation or a set of observations students collected. Ask students to choose between two claims and explain which is better supported. Avoid turning every starter into a full report.
You can also use the life science virtual labs to generate clearly labeled simulation data. Ask students to distinguish what the model shows from what would need testing with real organisms. For another short routine, try the Classroom Playbook.
My goal is an explanation students can defend and revise. If you want additional classroom materials, browse my Teachers Pay Teachers store; this starter is ready to use without a purchase.
Science and practice connections
The routine supports explaining and evaluating evidence, practices described in NGSS Appendix F. CER is used here as a writing scaffold, not as a substitute for a complete NGSS performance expectation. The photosynthesis explanation is consistent with OpenStax Biology 2e, section 8.1. The fictional data and lesson sequence are instructional examples created for this post.