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Common Core LiteracyGrades 6–8Science & Technical

RST.6-8.2: Central Ideas and Summaries in Science Texts

Also written as CCSS.ELA-LITERACY.RST.6-8.2 · Cluster: Key Ideas and Details.

All 29 Grades 6–8 Literacy Standards

The Official Wording

Determine the central ideas or conclusions of a text; provide an accurate summary of the text distinct from prior knowledge or opinions.

Common Core State Standards, Grades 6-8, Reading: Science & Technical Subjects · Read it at the source · Checked October 14, 2026

What RST.6-8.2 Means in Plain English

Students in grades 6 to 8 find what a science article mainly explains or concludes and retell it faithfully. A summary of an article on periodical cicadas keeps the 13- and 17-year cycles and the predator idea, and leaves out what the student already knew or thinks of bugs.

Fifth graders (RI.5.2) found two or more main ideas and summarized a text. Here the texts are lab reports and science articles, and the summary must hold to the author’s conclusions. In ninth and tenth grade (RST.9-10.2) students also trace how a text explains a complex process.

RST.6-8.2 I Can Statements

  • I can name the central idea or conclusion of a science text.
  • I can sum up a science text in a few accurate sentences.
  • I can keep my own opinions and outside facts out of a summary.

RST.6-8.2 Worked Example

The article builds to a conclusion and then a hypothesis, and the weak summary replaces both with an opinion and a family story.

Read the Story
Periodical cicadas spend 13 or 17 years underground as nymphs, sipping sap from tree roots. Then, in a single spring, a whole brood digs out within a few weeks, sometimes more than a million insects to an acre.The nymphs wait until the soil about 20 centimeters down warms to roughly 18 degrees Celsius. They climb a tree trunk, shed their skins and spend a few weeks as adults, mating and laying eggs, before they die.Biologists think the crowd itself is the defense. Birds, squirrels and even dogs gorge on cicadas, but they fill up long before they can eat them all, so most survive to breed. Scientists call this predator satiation.Why 13 and 17? One hypothesis notes that both are prime numbers, so the broods rarely line up with the population cycles of their predators, or with each other. A 13-year and a 17-year brood emerge in the same place together only once every 221 years.
A short passage written for this page.
Question: What are the central ideas of this article? Write an accurate summary in two or three sentences.
Not Yet“Cicadas are loud, creepy bugs that come out every 17 years. My grandpa says the last time they came out was the worst summer ever. They should stay underground, because nobody likes them.”It mixes in an opinion and a family story the article never gives, drops the 13-year broods, and skips the central idea that the huge crowd is the cicadas’ defense.
Meets the Standard“Periodical cicadas live underground as nymphs for 13 or 17 years, then a whole brood comes out within a few weeks, sometimes over a million to an acre. Biologists think the huge numbers protect them, because predators fill up before they can eat them all. One hypothesis is that the prime-number cycles also keep the broods from lining up with their predators’ cycles.”It keeps both cycle lengths, states the main conclusion and the hypothesis in the article’s own terms, still calls the hypothesis a hypothesis, and adds nothing the article did not say.
Question Stems to Use
What is the one idea every paragraph supports?What conclusion do the scientists in the text reach?Which details are needed to explain that idea, and which are extras?Did that sentence come from the text, or from you?Does your summary turn a hypothesis into a fact?

Common Mistakes with RST.6-8.2

Slipping in opinions

“Cicadas are creepy and should stay underground.”

Try this: Have students reread their summary and cross out any word a scientist in the article would not have written.

Adding what they already knew

“My grandpa says the last brood was the worst summer ever.”

Try this: Ask students to find each sentence of their summary in the article; anything they cannot locate gets cut, however true it is.

Turning a hypothesis into a fact

“Cicadas use prime numbers to dodge predators.”

Try this: Highlight hedging words like “think” and “one hypothesis” in the article, and make students carry the same hedge into their summary.

Where RST.6-8.2 Fits

Comes BeforeRI.5.2Determine two or more main ideas of a text, explain how key details support them and summarize it.
AlongsideRI.8.2Determine a central idea of a nonfiction text, trace its development and write an objective summary.WHST.6-8.2Explain a scientific topic in writing with precise terms and an objective tone, the summary’s habits at greater length.
Comes NextRST.9-10.2Find the central ideas of a science text, trace how it explains a complex process and summarize it accurately.

Practice RST.6-8.2

Quick Check

  1. How long do periodical cicadas live underground?
  2. What do biologists think protects cicadas from predators?
  3. How often do a 13-year and a 17-year brood emerge in the same place together?

RST.6-8.2: Other Names

RST.6-8.2CCSS.ELA-LITERACY.RST.6-8.2

Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved. Official wording from the Common Core State Standards PDFs at corestandards.org, last checked October 14, 2026. The explanation, I can statements, example, mistakes and practice on this page are EMStudio’s own, written beside the official wording. They are not part of the standard.