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Common Core ELA8th GradeReading: Informational

RI.8.2: Trace a Central Idea Across a Whole Text

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

All 41 8th Grade ELA Standards

The Official Wording

Determine a central idea of a text and analyze its development over the course of the text, including its relationship to supporting ideas; provide an objective summary of the text.

Common Core State Standards, Grade 8, Reading: Informational Text · Read it at the source · Checked October 14, 2026

What RI.8.2 Means in Plain English

Eighth graders follow one central idea from the first paragraph to the last and explain what each supporting idea adds to it. In a Panama Canal passage, the engineering facts turn out to be groundwork for the real point: the canal runs on rain. Then students summarize without opinion.

Seventh grade (RI.7.2) tracked two or more central ideas. Eighth grade narrows to one and asks how the supporting ideas build it, often toward a point the text reaches late. In ninth and tenth grade (RI.9-10.2) students show how specific details shape and refine that idea.

RI.8.2 I Can Statements

  • I can state a central idea that covers the whole text.
  • I can explain what each supporting idea adds to the central idea.
  • I can write a summary that leaves out my own opinions.

RI.8.2 Worked Example

The central idea does not surface until the third paragraph, and the weak answer stops at the first one.

Read the Story
Every ship that crosses the Panama Canal climbs a staircase of water. Locks raise each vessel about 85 feet to Gatun Lake, and more locks lower it to the sea on the other side.The locks use no pumps. Gravity lets water flow down from the lake into each chamber, and every crossing sends roughly 50 million gallons of fresh water out to sea.That water comes from rain. Rivers from the forested hills around Gatun Lake keep it full, so the number of ships the canal can handle depends on how much rain has fallen.In 2023, one of the driest years in Panama’s recorded history lowered the lake, and the canal cut daily crossings by more than a third. Lines of waiting ships stretched for days, and some owners sent cargo on much longer routes.Canal officials are now planning a new reservoir to store water for dry years. A shortcut used by ships from around the world still rises and falls with the weather in one small country.
A short passage written for this page.
Question: What is the central idea of the passage, how does each paragraph build it, and how would you summarize the text objectively?
Not Yet“The central idea is that the Panama Canal uses locks to lift ships 85 feet. It is an amazing invention, and more countries should build canals like it.”It promotes a supporting idea from the first paragraph to central idea and ignores the drought entirely. It also slips in two opinions that a summary should never hold.
Meets the Standard“Central idea: the Panama Canal runs on rain, so a drought in one small country can slow sea traffic worldwide. The first two paragraphs show that every crossing spends lake water, the third traces that water to rain, and the 2023 drought proves the risk. Summary: The canal’s gravity-fed locks drain about 50 million gallons from rain-fed Gatun Lake with every crossing. When a 2023 drought lowered the lake, crossings were cut by more than a third, ships were delayed or rerouted, and officials began planning a new reservoir.”The central idea fits the last paragraph as well as the first, each paragraph’s role is named, and the summary keeps every key fact and drops every opinion.
Question Stems to Use
What idea does the whole text keep returning to?Where does the central idea first become clear? What came before it?What does this paragraph add to the central idea?How is the idea different at the end than at the start?Which words in your summary are opinion? Cut them.

Common Mistakes with RI.8.2

Naming the opening topic as the central idea

“The Panama Canal lifts ships with locks.”

Try this: Have students test their central idea against the last paragraph first; if the ending does not fit, the idea is too narrow.

Listing supporting ideas without connecting them

“It talks about locks, water, rain and a drought.”

Try this: Ask, for each paragraph, “What does this add to the central idea?” and require the answer as a single linking sentence.

Opinions in the summary

“The canal is amazing, but it was careless not to plan for droughts.”

Try this: Have partners swap summaries and underline every word that judges, praises or blames, then rewrite those sentences using only facts.

Where RI.8.2 Fits

Comes BeforeRI.7.2Find two or more central ideas, trace how each develops and give an objective summary.
AlongsideRL.8.2Trace a theme across a story and its link to the characters, setting and plot.RST.6-8.2Find the central ideas or conclusions of a science text and summarize them accurately.
Comes NextRI.9-10.2Show how a central idea emerges and is shaped and refined by specific details.

Practice RI.8.2

Quick Check

  1. What is the central idea of the Panama Canal passage?
  2. Why does the passage explain how the locks work before it mentions rain?
  3. Which belongs in an objective summary: “Lines of waiting ships stretched for days” or “The canal is an amazing invention”?

RI.8.2: Other Names

RI.8.2CCSS.ELA-LITERACY.RI.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.