How to Get Rid of That Junk in Your Classroom

If you are like most teachers I know -  you save everything.
I am pretty sure you know what a junkyard is, but how about a junk car?
Let's just say it like this- a car made of junk. Now, how is this going to work, you ask. Stick with me for some hints and tricks as we tackle a STEM challenge using junk you already have- which will help you get rid of some of it, too!

STEM Challenge: Build a car using basic materials and a little bit of junk.
This STEM challenge originated a few years ago as I looked for something my third graders could build. I came into the lab realizing I had nothing prepared for them. Dangerous way to begin a teaching day, I know, but it happens. I stood there thinking and had one of those brain-pop moments - let's build boats!  I started opening cabinets. I laid a pile of weird items on my supply table and told kids to pick what they thought they would need to make a boat.....yeah well, as crazy at that sounds it worked and that STEM challenge is now my number one seller in my store.

So, why wouldn't this work for.....CARS!

STEM Challenge: Build a car using basic materials and a little bit of junk.
So, I promise I did the same thing. I started pulling a bunch of JUNK out of the cabinets and offered items to the kids to piece together and build a car that will roll.

Now, I know what you are thinking!

How is this STEM? 

Well, It's the ultimate in STEM - it's making do with what you have and making it work!

Think about it! Do you know the story of Apollo 13? That spacecraft was doomed. An explosion left the astronauts with a decreasing oxygen supply and only the engineers on earth saved them. How? By piecing together a bunch of junk that the astronauts had on board and building a device to fix the oxygen problem. (Duct tape might have been involved!)

So, why can't we build a model of a car using cups, waxed paper, florist foam, tape, straws, and cardboard? Easy answer- You can build a car using whatever junk you can gather! (A little off topic, but you need to know that I use the word 'junk' in a joshing way. All of the materials are fabulous items, but you might not think them as a building material. Kids love it, however!)

So, off we went on round 1 of building cars. The predominant material kids used in our first attempt at this challenge was florist foam. And that was because I had access to a large amount of it. They made block shaped cars out of that foam. Since this was such an unusual material, of course every team wanted to try it. I still remember hearing a kid say,

"Wow, this stuff is so easy to stab!" 

Uh, not exactly what you want to hear in your classroom.

Ready for some more hints, advice, or tricks?


When we repeated this challenge and I did not offer foam! So, first little piece of advice about using junk- be careful with the kind of junk. Some things work great and some things can be too messy, too costly, or too hard to manipulate. Florist foam is a great material, but not my first choice after using it in the past!

For this repeat of  building cars I put out an array of 10 items and the kids had to choose from those. (Although this was a random ten things I had in the cabinets I did think carefully before pulling them out!)

STEM Challenge: Build a car using basic materials and a little bit of junk.
One of the most difficult parts of building a car is attaching the axle and then the wheels and making them roll. In the photos above you can see a crooked car because the axles are inserted in the car body at different angles. What a great lesson that was! 

Hint #2- Talk to kids about lining both axles up better!

STEM Challenge: Build a car using basic materials and a little bit of junk.
There always seems to be a student or two that knows to insert a dowel stick inside a straw so the axle will turn. Pretty genius! The two photos above are showing that little trick. You can tape down the straw and the wooden dowel stick still rolls inside it.

HINT #3: 

You might notice that some of our cars use bottle caps as wheels. They work great. Just one problem: the holes. I have tried a lot of things and drilling the hole is best. It's not easy, to be honest. They crack sometimes and centering the hole is hard. Keep reading for more about wheels!

STEM Challenge: Build a car using basic materials and a little bit of junk.
Here's a little known fact about building a car. The placement of the axle will determine the size of the wheels needed.  So, kids should get the car built and axle in place BEFORE making wheels.

(If you are counting that was hint #4!)  

Go all the way back to the first photo of a car made from cups. Notice the size of the wheels. The axle is so high up on the body of the car that small wheels won't touch the ground! What a great lesson that was, too!

Above you can see kids with several more wheel problems. Mmmmmmm... the wheels have to be the same size and they need to be round! See the little wheel that is flat on one side? That team told me they had a flat tire!

HINT #5: 

Cardboard makes the best wheels! Trace something round, cut them out, and use a screwdriver to make the center hole. (The TEACHER uses the screwdriver. And if you don't do it, kids will try poking that hole with scissors! You can also use the point of a compass or a pencil to make holes.)

STEM Challenge: Build a car using basic materials and a little bit of junk.
Finally, when kids have cars that are somewhat rolling they can decorate. This most recent batch of kids make the cutest accessories for their cars. Take a look at those exhaust pipes!

Kids love this challenge! Every part of it! It is very competitive to see who can make a rolling car. I love it because I grab materials and throw it out for the groups to gather. One last hint: the simpler the materials, the better!

So, there you have it! 

A fabulous and fun STEM challenge, full of learning. The cars are made of easily gathered classroom "junk" which can be re-used. I hope my hints will give you a few ideas and if you need more details you can always check my store.  Here are some more photos!

STEM Challenge: Build a car using basic materials and a little bit of junk.


  1. This is a Genius Idea!!! I have a ton of leftover "junk" in my supply closet from Christmas decorations, craft activities, and party supplies.

    1. Exactly! Some of my most popular STEM challenges were born from just grabbing items randomly- and it almost always includes straws! Thanks for visiting!

  2. So glad your class had so much fun learning. I recently did this same thing letting the kiddos build bridges. I put out different materials a few days in a row and each day was a new challenge. I threw in some goats, too, to see how much the bridge would hold, and because we were retelling the Three Billy Goats Gruff :) Thanks for post. Kathleen


Back to Top