What this standard means: Determine the main idea of a text and tell the key details that support it. You will read two short texts today. Neither one tells you its main idea, so you have to build it yourself out of the details.
Use these three steps every time:
1. Read the whole text. Do not stop after one sentence.
2. Name the key details. What are the most important things the text tells you?
3. Test your idea. Ask: do ALL the key details point to it?
Watch out for two traps. An idea can be TOO SMALL, which means it fits only one detail, so it is a detail and not the main idea. An idea can also be TOO BIG, which means it says more than the text really says. The main idea fits every key detail, and nothing more.
After the two texts, each question gives you a new set of details to practice on. Use the same three steps on every one.
Before you download
What you get, and who it’s for
Everything below is measured from the actual lesson and the actual file. Nothing here is an estimate.
Time to run
About 25 minutes. 10 min lesson, then 15 min of practice.
In the download
9 printable pages: the full lesson, the worked examples, the visual models, and 8 practice questions with space to work. A teacher answer key is included at the end, so the student pages come first and it is still ready to hand out. The lesson’s worked examples do show their solutions, because that is how they teach.
Question set
The download carries all 8 questions. The page shows 3 of them as a sample.
Question format
Every question is multiple choice. Students show their work on the page.
Dates
Published August 5, 2026. Not revised since.
The sample intervention
See a real lesson for RI.3.2
A real intervention, not a generic worksheet.
RI.3.2
Finding the Big Idea: Sea Turtles and National Parks
Determine the main idea of a text and tell the key details that support it.
You will read two short texts today. Neither one tells you its main idea, so you have to build it yourself out of the details.
Use these three steps every time:
1. Read the whole text. Do not stop after one sentence.
2. Name the key details. What are the most important things the text tells you?
3. Test your idea. Ask: do ALL the key details point to it?
Watch out for two traps. An idea can be TOO SMALL, which means it fits only one detail, so it is a detail and not the main idea. An idea can also be TOO BIG, which means it says more than the text really says. The main idea fits every key detail, and nothing more.
After the two texts, each question gives you a new set of details to practice on. Use the same three steps on every one.
One Big Idea, Three Details
Arrows point from the details up to the main idea, never the other way. If a detail does not point to your idea, your idea is not the main idea yet.
A green sea turtle slips into the water off a beach in Florida. Months later, that same turtle is swimming near an island thousands of miles away.
Sea turtles follow the same ocean routes year after year. They can sense where the sun is and feel Earth's magnetic field, an invisible force that wraps around the planet. And many females come back to the very beach where they hatched to lay their own eggs.
Scientists are still amazed by this. A turtle may swim through deep, dark water for weeks and still turn at the right place, the way you might walk the same route to school every morning without thinking about it. Years may pass before a female returns to her home beach, but she still finds it.
Three details, one big idea
Sea turtles follow the same ocean routes year after year1. They can sense where the sun is and feel Earth's magnetic field2, an invisible force that wraps around the planet. And many females come back to the very beach where they hatched3 to lay their own eggs.
Evidence 1: the same ocean routes, every single year
Evidence 2: the sun and magnetic field guide them
Evidence 3: back to the beach where she hatched
All three highlighted details answer the same question: how does a sea turtle know where to go? That is your clue to the main idea.
Worked exampleWATCH ME FIND THE MAIN IDEA
Step 1. Name the key details.
- Sea turtles follow the same ocean routes year after year.
- They sense the sun and Earth's magnetic field, like a built-in compass.
- Females come back to the very beach where they hatched.
Step 2. Ask what all three have in common. Every one of them is about the same thing: knowing where to go.
Step 3. Test an idea. How about "Sea turtles lay eggs on beaches"? Does detail 1 point to it? No. Does detail 2 point to it? No. Only the last detail fits, so this idea is TOO SMALL. It is a detail, not the main idea.
Test another idea: "Sea turtles have amazing ways of finding their way in the ocean." Detail 1 points to it. Detail 2 points to it. Detail 3 points to it. All three fit, so this is the main idea.
At Yosemite National Park, a small sign near a meadow asks visitors to stay on the trail. It looks like a plain little sign, but it is doing an important job.
Park rules ask people to leave plants, rocks, and animals alone. When visitors stay on the trail, the tiny flowers along the path get a chance to grow instead of being crushed.
Rangers also count animals every year. They may count bighorn sheep on a mountain or frogs in a pond. If a number drops, rangers know something is wrong and can act before those animals disappear.
Some parks even guard the dark. Bright lights confuse owls, bats, and other animals that move at night. So certain parks turn off extra lights and shade the ones they keep, leaving the night sky as dark as nature made it.
Every detail points the same way
How it keeps nature safe
Rules: leave plants, rocks, and animals alone
Living things do not get harmed
Rangers count the animals every year
Trouble is spotted before it is too late
Some parks keep the night sky dark
Owls and bats can still hunt at night
Three different details. Read the right column: each one is another way of keeping nature safe. That is the big idea they all support.
Worked exampleNOW YOU TRY THE SAME THREE STEPS
Step 1. Here are the key details from the national parks text.
- Park rules ask people to leave plants, rocks, and animals alone.
- Rangers count animals every year to check that they are healthy.
- Some parks keep the night sky dark so night animals are not confused.
Step 2. What do all three have in common? Stop and think of an idea before you read on.
Step 3. Test this idea first: "National parks are fun to visit." Does the rules detail point to it? Does the animal counting detail point to it? Does the dark sky detail point to it? None of them do. The text never says this, so the idea is TOO BIG.
Now test this one: "National parks do many things to keep nature safe." Rules keep nature safe. Counting animals keeps nature safe. A dark sky keeps nature safe. All three details fit, so this is the main idea.
Practice questions
1
Which detail best supports the idea that sea turtles know how to travel well?
Scientists watch these animals.
Some sea turtles eat sea grass.
They use the sun and Earth’s magnetic field.
Their hard shells help protect them.
2
A student wrote: 'The main idea is that sea turtles have hard shells.' What detail shows this is too small?
The text says sea turtles are birds.
The text is about jellyfish only.
The text has only one sentence.
The text gives several details about travel, not just shells.
3
Which main idea best matches this group of details: 'Scientists watch these animals. They learn where they travel. They learn how to keep them safe.'
Scientists study sea turtles to help keep them safe.
Scientists only watch animals for fun.
Scientists like beaches best.
Scientists build trails in parks.
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