Common Core LiteracyGrades 9–10Science & Technical

RST.9-10.2: Central Ideas and Complex Processes

Also written as CCSS.ELA-LITERACY.RST.9-10.2 · Cluster: Key Ideas and Details.

The Official Wording

Determine the central ideas or conclusions of a text; trace the text's explanation or depiction of a complex process, phenomenon, or concept; provide an accurate summary of the text.

Common Core State Standards, Grades 9-10, Reading: Science & Technical Subjects · Read it at the source · Checked October 14, 2026

What RST.9-10.2 Means in Plain English

Ninth and tenth graders find a science text’s main conclusion, follow its account of a complex process step by step and summarize it accurately. A passage on how kidneys filter blood is only summarized right if the step where almost everything is taken back survives.

In grades 6 to 8 (RST.6-8.2), students summarized a text apart from their own opinions and prior knowledge. Ninth and tenth grade add tracing a process through its steps. In grades 11 and 12 (RST.11-12.2), students paraphrase complex concepts in simpler terms that stay accurate.

RST.9-10.2 I Can Statements

I can state the main conclusion of a science text.
I can trace each step of a process in order.
I can summarize a process without dropping a key step.

RST.9-10.2 Worked Example

The passage explains how a kidney filters blood, and the weak answer treats the kidney as a strainer and skips the step that does most of the work.

Read the Story

Your two kidneys hold about two million tiny filtering units called nephrons, and the body’s whole blood supply passes through them many times a day.Filtering starts in the glomerulus, a knot of capillaries. Blood pressure pushes water, salts, glucose and urea out through the capillary walls into a cup called Bowman’s capsule, while blood cells and large proteins stay in the blood. The fluid collected there is called filtrate.The kidneys make about 180 liters of filtrate a day, many times the volume of all the blood in the body. They could not keep that up if the filtrate simply left as urine.As the filtrate flows along the nephron’s tubule, the cells lining it pull back nearly all of the glucose, most of the salt and about 99 percent of the water, returning them to the blood. Much of the urea stays in the tubule.What is left drains through collecting ducts as urine, about 1.5 liters a day. A hormone called ADH signals the collecting ducts to hold back more water when the body is short of it, so a dehydrated person makes less, darker urine.

A short passage written for this page.

Question: What is the central conclusion of the passage? Trace the process it explains in order, then write an accurate two-sentence summary.

Not Yet“The kidneys filter your blood to make urine. Blood goes into the kidney and the waste comes out. Summary: Kidneys are filters that take the bad stuff out of your blood.”It describes the kidney as a strainer that pulls out only waste, which misses the passage’s main point: the kidney filters out useful and waste substances alike, then takes back almost everything. It skips reabsorption and ADH, so the summary is not accurate.

Meets the Standard“The central conclusion is that the kidney cleans blood in two stages: it filters out nearly everything small, then takes back almost all of what the body needs. In the glomerulus, blood pressure pushes water, salts, glucose and urea into Bowman’s capsule, leaving cells and proteins behind. Of the ‘about 180 liters of filtrate a day,’ the tubule returns nearly all the glucose and ‘about 99 percent of the water,’ while much of the urea stays. The rest drains out as urine, and ADH adjusts how much water is kept. Summary: Nephrons filter water and small molecules out of the blood, then reabsorb almost all the water, glucose and salt. The leftover fluid leaves as about 1.5 liters of urine a day, with ADH holding back water when the body runs short.”It states the two-stage conclusion, traces each step in order with the text’s own figures, and its summary keeps the reabsorption step and the numbers that make the process surprising.

Question Stems to Use

What happens first, and what makes it happen?Which step undoes most of the step before it?What do the two numbers, 180 and 1.5, tell you about the process?Which step would a quick reader skip? What would the summary lose?Does your summary say anything the text does not?

Common Mistakes with RST.9-10.2

Summarizing from prior knowledge

“Kidneys take the bad stuff out of your blood.”

Try this: Have students check every sentence of their summary against the passage and cross out anything the passage does not actually say.

Dropping the step that surprises

A summary that goes straight from filtering to urine, with no reabsorption

Try this: Ask students to number the steps in the margin, then confirm their summary names each step, especially the one that reverses an earlier one.

Naming the topic as the conclusion

“The central idea is the kidneys.”

Try this: Have students finish the sentence “The text shows that the kidney…” with a claim the numbers in the passage could prove.

Where RST.9-10.2 Fits

Comes BeforeRST.6-8.2Find the central ideas of a science text and summarize it apart from prior knowledge or opinion.

AlongsideRI.9-10.2Trace how a central idea emerges and is refined by details, with an objective summary.WHST.9-10.2Explain a scientific process in writing with precise terms, clear transitions and a conclusion.

Comes NextRST.11-12.2Paraphrase complex concepts and processes in simpler but still accurate terms.

Practice RST.9-10.2

Quick Check

What is the central conclusion of the passage?
The kidney cleans blood in two stages: it filters out nearly everything small, then takes back almost all of what the body needs.
Where does filtering start, and what stays in the blood?
In the glomerulus, a knot of capillaries. Blood cells and large proteins stay in the blood.
Why do the kidneys make about 180 liters of filtrate a day but only about 1.5 liters of urine?
The tubule returns nearly all the glucose, most of the salt and about 99 percent of the water to the blood.

RST.9-10.2: Other Names

RST.9-10.2CCSS.ELA-LITERACY.RST.9-10.2