Keeper or Not a Keeper?

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SWBAT use measurement guidelines they create to measure with nonstandard units.

Big Idea

Students measure fish to determine if the fish is a keeper or not a keeper. In doing so, they also tackle rigorous measurement questions!

Setting Up the Learning

5 minutes


We looked at how one person measured a fish yesterday and we saw that he got so many different answers! We made a list of the mistakes that we saw. Today we are going to use these mistakes to help us write guidelines, or rules, we need to use as we measure.



We measure all the time in real life. When your mom sees if you have a fever, she is measuring how hot or cold you are. When you check the clock, you are measuring how many minutes something takes. Fishermen have to measure fish to determine if they are a keeper or not. When we measure how long something is, we are measuring length


Objective :

Your thinking job today is: What rules can we write to help other people learn how to measure?

Opening Discussion

10 minutes

Students use the chart from yesterday (see attached picture: Fisherman's Journal) to create the letter for today!


I'll say: "We are going to write a letter explaining all of the guidelines everyone should follow to make sure this fisherman doesn’t make any mistakes next time. I left some space at the bottom of the letter for you to help me write the guidelines, or rules."


We are creating a letter so students get practice articulating their thinking in writing, a strong component of Common Core. This is also a way to introduce the idea of using a variety of sources to create a letter (CCSS.ELA-Literacy.W.1.8).


I’ll show each fish and have students do a partner talk.

Turn and Talk: Tell Mr. Johnson what he did wrong on this one and how he can fix it. The sentence stem you can use is “When you measure next time, you need to ___”.

I’ll listen in to make sure students use affirmative language, and choose an exemplar to put in our letter. Then we will reread the letter as a class.  (See attached picture: Letter for how our letter turned out!)

Student Share

12 minutes

During this portion of the lesson, I'll have students apply what they told our principal to how we will measure today. I will give them a different kind of fish to measure today, one that needs to be 3 inch tiles long to be a keeper.

All the students will measure the first fish in the Independent Practice documents (see that section). I will be looking for students who are still showing misconceptions. 

See video for an example of how this looked in my classroom! Take note of what students were supposed to do when they finished.


After students measure that fish, we will look at one student's work and discuss how it followed all of the guidelines we gave our principal!

Independent Practice

15 minutes


1. Students measure each fish and label its length.

2. Students cut out the fish. 

3. Students glue fish into keepers and not keepers (this is a review of K.CC.C.7, "Compare two numbers between 1 and 10 presented as written numerals" and will prepare them for future lessons on comparing numbers (1.NBT.3)


Extension: Students take another copy of the fish and put them in length order!

*See attached pictures (Completed Keeper Sort and Exemplar Fish Ordering) for examples of student work!


5 minutes

Partner talk: Share your sort with a partner. Did you get the same answers? Check your partner’s work.


We will then package up the letter and put it in the envelope to send away!