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cer strategies

Five strategies for writing killer evidence to support a claim in science


If I told you the Pixar movie Cars is all about learning how to be selfless, could you give me evidence from the movie to prove it? Of course you could! Can your middle school students? Probably. Cars is a story that’s entertaining and easy to follow. But let me tell you what… trying to get middle school students to use data evidence to support their claim in science is a whole different beast. 

The truth is, a lot of students struggle to find and use evidence in science correctly. So, how do we fix it? 

The struggle with CER

I hated teaching CER strategies in science for a long time. No matter how many times I said, “use evidence to support your claim,” very few kids gave me quality evidence. Oftentimes, my students had the correct ideas without articulating them with correct evidence. 


I was looking for hard evidence, numbers, comparisons and instead getting evidence that sounded more like this: 

The penny with water only dropped on it held the most water. 

It wasn’t specific enough. I could tell my 7th and 8th graders were really trying. Hard. But it just wasn’t enough. 

If this sounds like you, and your students, this evidence writing lesson will help you so much!

I used commercials to get kids used to the idea of being specific and paying attention to details. If you haven’t heard of using commercials to teach CER, Beakers and Ink gives some very fun examples! 

It worked! Kids loved it, and it did hit the point home that they needed to have evidence to support their claim. But when I asked for evidence in a scientific context, it didn’t translate well.

All evidence is not created equal

Evidence is unassumingly tricky for science teachers. Maybe it’s just me who thinks that, but I doubt it. In my opinion, there are a few reasons for this. Students are expected to support their claim with evidence in science and ELA. The difference is in the technicality of the evidence we’re asking students to find and use. 

I’ve walked into more ELA classes than I can count where the teacher was explicitly teaching how to find and use specific types of evidence to support a claim.

If students are supporting their claim based on character traits, the teacher spends a lot of time teaching what examples of character traits are, where to find them in a story, and how to use them to support their claim.

If students are reading nonfiction to find evidence to support a claim in their writing, they learn strategies to do so. 

Struggling to get your students to write good evidence to support their claim in science? Grab the perfect lesson here!

Evidence in Science is different

Using evidence to support a claim in science is so different because teachers give examples of what evidence should look and sound like. Rarely do we explicitly teach kids how to draw quality evidence from data. The kind of evidence we want in science uses math skills. Our students don’t explicitly learn that.  

I think this is why my students did so well with commercials. They knew how to find evidence in an ELA context – the commercials. I still use commercials for a good claim, evidence, reasoning example. But, I’ve learned that it’s an engagement tool and science teachers need to follow up with some explicit instruction for science evidence. 

The six key to writing evidence

So, I’ve convinced you that students need a little more help from us in terms of writing evidence. It’s time to teach your middle school science students how to really draw information from data! 

I’ve come up with six different types of evidence that students can pull from a data table to support their claim in science. My goal is always to get students to use hard numbers in their evidence. Think of the following as claim, evidence, reasoning sentence starters… but these ones are just for the evidence portion. 

Use measuring words.

Obviously this isn’t a sentence starter and isn’t an official strategy. Asking students to use measuring words helps them write evidence better. Making sure students include words like faster, farther, more, or increase helps them form correct evidence.

1. Compare the average.

Students can (and should) find the average of all their trials at the end of their investigation and then compare. An example of this would be: 

On average, the 16 pound bowling ball knocked down four more pins than the 10 pound bowling ball. 

2. Compare the trials.

By looking at the whole trials instead of the individual numbers, they can see how many total trials had outcomes that went one way or another. An example of this would be: 

Three out of four trials showed strawberries grown in direct sunlight produced more strawberries than those grown in shade. 

3. Find the “at least”.

The goal for this example is to show the difference between results in the trials. It’s a little tricky because you want to also compare trials, but here’s an example. 

In five out of six trials, students who drew their vocabulary words remembered at least 16% more words on a quiz than students who did not draw them. 

4. Look at individual trials.


Here, students look at the result from one trial to use as evidence to support their claim in science. Be careful, sometimes students will use this to make their point instead of supporting the true outcome. 

Trial three showed mice who ate sugar traveled through the maze 15 seconds faster than the mice who didn’t eat sugar. 

5. Tell the total.

As students are looking at their data table, have them look at the average totals and simply use those totals as evidence. Of course, we’d like to see students write more, but this is a great starting point. Here is an example: 

The penny held an average of 21.5 drops of soapy water and 37.2 drops of regular water. 

Don’t these five tips sound awesome? Save yourself some time and and grab this zero prep lesson to help your students master writing evidence to support a claim in science!

Use evidence to support a claim in science

I often think we forget students need to grapple with content more than once. Maybe forget isn’t the right word, but we think because we told our students, showed them an example, or know they learned it somewhere else, they got it. Even if we do tell them over and over, there’s a good chance they still won’t remember it.

So instead we tell them to “use evidence to support their claim” without giving them quality tools to do it successfully. 

My charge to you is this. Spend just a little bit of time teaching your students evidence skills so they can successfully use that evidence to support their claim in science. 

Reading & Writing in Science, Scientific Inquiry, Uncategorized