Common Core LiteracyGrades 11–12Science & Technical

RST.11-12.9: One Explanation from Many Sources

Also written as CCSS.ELA-LITERACY.RST.11-12.9 · Cluster: Integration of Knowledge and Ideas.

The Official Wording

Synthesize information from a range of sources (e.g., texts, experiments, simulations) into a coherent understanding of a process, phenomenon, or concept, resolving conflicting information when possible.

Common Core State Standards, Grades 11-12, Reading: Science & Technical Subjects · Read it at the source · Checked October 14, 2026

What RST.11-12.9 Means in Plain English

Juniors and seniors build one coherent explanation of a process from readings, experiments and simulations, and settle conflicts between the sources when the evidence allows. A textbook says short-day plants respond to day length; a poinsettia experiment and a simulation show it is the unbroken night that counts.

Ninth and tenth grade (RST.9-10.9) compared a text’s findings with other sources and their own experiments, noting agreement and contradiction. Grades 11-12 go further, combining everything into one account and resolving the conflicts. This is the last band of the line, the synthesis college and career readiness demands.

RST.11-12.9 I Can Statements

I can combine readings, experiments and simulations into one explanation.
I can find the source that tests two explanations against each other.
I can explain why a conflicting source once seemed right.

RST.11-12.9 Worked Example

The sources are invented for this page, though the plant science is real. The textbook and the experiment seem to disagree, and only the strong answer settles why.

Read the Story

Source A, a biology textbook: Short-day plants, such as poinsettias, flower when the days grow shorter than a critical length in fall.Source B, a class experiment with three groups of poinsettias over eight weeks: 10 hours of light and 14 of darkness, bracts turned red and plants flowered; 13 hours of light and 11 of darkness, no change; 10 hours of light and 14 of darkness with a ten-minute light flash at midnight, no change.Source C, a plant-growth simulation: the virtual short-day plant flowers only when its longest unbroken dark period passes a set threshold; splitting one long night into two short ones stops flowering even though total darkness stays the same.Source D, a nursery owner’s logbook: poinsettias need 14 hours of uninterrupted darkness every night from early October; last year, the row of pots beside the office window, where a desk lamp stayed on late, never turned red.

A short passage written for this page.

Question: What does a short-day plant actually respond to, the length of the day or the length of the night? Combine all four sources into one explanation, and resolve the conflict between them.

Not Yet“Source A says short-day plants flower when the days get shorter, and the experiment shows the 10-hour group flowered while the 13-hour group did not. So shorter days make poinsettias flower, and the nursery should turn off the lamp.”It takes the textbook at its word and reads the experiment only where it agrees. The midnight-flash group also had a 10-hour day and did not flower, which the answer skips, so the conflict is never noticed, let alone resolved.

Meets the Standard“Short-day plants respond to the length of unbroken darkness, not daylight. The experiment shows it: the midnight-flash group got the same 10-hour day as the group that flowered, yet stayed unchanged, so a short day was not enough. The simulation confirms it from the other side, since splitting one long night stops flowering even when total darkness is unchanged. The nursery logbook shows the same thing in practice: one late lamp broke the night, and that row never turned red. That resolves the conflict with the textbook. In nature, short days and long nights always arrive together, so describing these plants by day length predicts when they flower in fall, which is why the name stuck. Only when a night is interrupted, as in Sources B, C and D, do the two explanations come apart, and night length is the one that holds.”It builds one explanation from all four sources, leans on the experiment that separates the two ideas, and resolves the conflict by showing why the textbook’s version works in nature and fails under a night break.

Question Stems to Use

Where do two sources seem to disagree? State the disagreement exactly.Which source tests the two explanations against each other?Can both sources be right under some conditions? Which ones?What does each source add that the others do not?How would you explain the process in one paragraph that fits every source?

Common Mistakes with RST.11-12.9

Reading the sources in a row instead of together

“Source A says … Source B says … Source C says … Source D says …”

Try this: Have students write the one-paragraph explanation first, then tag each sentence with every source that supports it.

Siding with the textbook by default

“The textbook says day length, so the experiment must have gone wrong.”

Try this: Ask which source actually tests the two explanations against each other, and give that source the most weight when they conflict.

Declaring a winner without explaining the loser

“The textbook is wrong.”

Try this: Require students to explain why the weaker source still seemed right, naming the conditions under which both explanations predict the same thing.

Where RST.11-12.9 Fits

Comes BeforeRST.9-10.9Compare a text’s findings with other sources and experiments, noting where they agree or contradict.

AlongsideRH.11-12.9Integrate primary and secondary sources into one coherent account, noting discrepancies among them.RST.11-12.7Integrate data, video and text in diverse formats to address a question or solve a problem.

Comes NextWHST.11-12.7Synthesize multiple sources in a research project that answers a question or solves a problem.WHST.11-12.2Write an explanation of a scientific process in which each idea builds on the one before it.

Practice RST.11-12.9

Quick Check

Which group in the class experiment separates the day-length and night-length explanations?
The midnight-flash group: it had the same 10-hour day as the group that flowered but did not change, because its night was broken.
What does the simulation add?
It shows that splitting one long night into two short ones stops flowering even when total darkness stays the same.
Why does the textbook’s description still predict flowering in nature?
In nature, short days and long nights always come together, so day length works as a stand-in until a night is interrupted.

RST.11-12.9: Other Names

RST.11-12.9CCSS.ELA-LITERACY.RST.11-12.9