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How to Add a Twist to any STEM Challenge

Are you ready for a frequently asked question? I decided to start a series of these! Last month was all about tips to get you started in STEM- especially if you are overwhelmed. This month the question is: “How can I change a STEM Challenge to make it more challenging or just add a little zest to it?” What a great question and I have the perfect answer and some samples to show you!

Let’s Be Honest

Teaching the same lessons can just be a little tedious. I mean, year after year, the same things. Now, let’s also quickly add that STEM is a tad different. The groups of students are going to make any STEM event different- group dynamics, designs, and failures are always going to work differently. But do you still find yourself wanting to change things up a little anyway? I sure do! This is why I tried adding this little twist!

There are many reasons for adding something to a STEM Challenge! I have several more:

  • It helps with the use of materials.
  • It introduces several new skills.
  • It is so intriguing to watch and the kids LOVE it.
  • It creates more problem-solving!
  • It creates a need for a great design idea.
  • The ability to improve models was dependent on it.

SO, what is IT?

The Budget Feature

Yes, it is the budget feature. So let’s get serious about how to add this little twist to any challenge. Here is what you need:

  • Fake money
  • Cash register (optional, but it is fun)
  • A price list
  • A spreadsheet for students
  • Calculators (also optional)
  • STEM Mart (this is what we call our shopping table)

The first time I tried this was for a simple reason. Students were wasting supplies. I had allowed teams to decide what they needed from an array of items. Well, they picked everything and in quantities that were just over the top!

So, I added a budget. Students had to purchase their materials and had a limited amount of money.

When I started handing out little five-dollar bills the students went a little silly-nuts. They were quickly right into the middle of listing materials and bargaining for what they could afford. 

Sound fun?

You bet it is! I have some sample challenges to show you and some ideas for how we tackled each and what we learned from using a budget.

The Build a Boat STEM Challenge is a runaway hit with my students. They cheer when they see Boats on our agenda and your students will too! There is just something about building that boat and holding your breath to see if it will float (it will) and then counting weights into it to see how long it will stay floating.

Use of Materials

This challenge is the first one I added the budget feature to. And it was because of the way students were using so many items. My directions were: “There are 10 different items from which to choose. Make good choices based on your designs.” Well, they chose everything! Even if it wasn’t labeled in their designs they grabbed everything. Students told me they “might need” some of the items. BAM! I invented the budget.

I placed a price tag on every item and told them they could only spend $7. This changed everything.

TIP: I always price items based on need. The things that I know will be necessary are more expensive. When students notice this we stop and have a little chat about supply and demand. 

THE CHALLENGE: Building Boats– students build a boat that floats and they test it with weights. I have seen several boats that held 500+ pennies. Trust me, that is a lot of weight!

New Skills

 The introduction of the budget adds so many skills to the STEM Challenge.

To complete their price list students must calculate quantities of materials and then get a subtotal. When they go shopping for more they have to recalculate the total. We use calculators most of the time, but this depends on the prices. Often, we can do all of the math without a calculator. 

I also use money and this is another lesson- how to buy something. And how to count back change. I check their math and then have them watch as I count out the change and then count it back to them. Real-life meets a math lesson!

TIP: I always start by giving the teams big bills and no coins. This helps me know which teams need some added encouragement to hand the cashier (me) the right amount of money. Often kids will just give me all their money! I hand it back and tell them to give me only what is needed.

THE CHALLENGE: Flood Barriers– students experiment with absorbent materials and then choose the one that worked best to build their own barrier to stop a flood.


This is my favorite part of the budget feature. Students must work together to determine which design they will use and then list the right materials for it. They bargain over whether they need 3 or 4 straws. I often hear them say, “Well, the craft sticks are only 25 cents.” I have even had teams that each drew a sketch and calculated the amount their individual designs would cost and then they build the one that is the least expensive!

TIP: Be sure students know to have a great sketch first and then plan for the materials. I insist they show me the design sketch before they can go shopping.

THE CHALLENGES: The three in the above photo are all platforms. We either do the straw, craft sticks, or paper platforms. They all must be a certain height and hold weight.


This is another amazing part of the budget feature. As students begin to build their design they will run into something that is not working correctly. They need more materials. But, what if they do not have much money left? This becomes a huge dilemma which makes the teams have to re-think what they are building and make decisions based on what they can change. They will often bring unused items back to STEM Mart and trade for something that will work better. They might also have to purchase something that they can use in a different way to solve the construction problem. Example: Straws are usually less expensive than craft sticks and since they are longer they will sometimes work better.

TIP: What if a team is out of money and cannot get their structure to work? Should you give them more money? I don’t –  because in real-life situations you would have to “make it work” and that is what I tell them. I do allow them to go to other teams and see if any group has spare parts or unused parts they will give them.

THE CHALLENGEBuild a Volcano – students construct a volcano model that has a small bowl in it. We pour baking soda in the bowl and then add vinegar as part of the demonstration of an eruption. My third graders love this challenge!

Designing (Because of the Budget)

This is such an important part of the budget feature. Students must have a neatly drawn and a labeled sketch of their idea. They need to label the sketch with the materials that will be used. This information is then transferred to their cost sheet so they can determine a total. The cost sheet is their shopping list.

Students visit STEM Mart with the shopping list and design sketch. I check the sketch to make sure they have thought through the challenge and then check their cost sheets. If the cost sheet is correct they load their shopping carts with the items chosen.

TIP: I allow students to load their shopping carts. They are really diligent about only picking out the exact amounts of the materials they have purchased. Our shopping carts are plastic shoeboxes.

THE CHALLENGE: Egg Cars– Students build a rolling car that must transport an egg down a ramp. We start with a plastic egg and add a real egg if the car seems to be working well.

Can you improve?

This is another important part of the budget challenges. Can students improve their models? The answer is YES! But, only if they have money left over to purchase more materials.

As I check their cost sheets I always advise groups to get less of some of the items. When a group says they need 6 cups or 10 pieces of paper I will tell them it is better to get half of the amount. They can always come back later.

TIP: You will always have groups that think they have to spend all the money. If I have a team that does this on their first shopping trip I will offer advice. It is always better to have money left after that first trip to STEM Mart. I help them adjust their cost sheets and give them some money back!

THE CHALLENGE: Gliding Bridges – students must choose a soil composition that will create the most sturdy area for building the end supports for a bridge system. Their passenger car is pulled from one side of the bridge to the other with a string. 

Adding a Budget

I have a few more tips for you about adding a budget!


  • Make the budget limit a reasonable amount. I usually have a $7-10 limit. You want this to be an amount that will allow teams to get what is needed. To make a challenge harder, make the limit lower.
  • Price items based on how popular they will be. I have even made different colors of paper cost different amounts- based on what we are building.
  • Allow exchanges of items that have not been used. You can exchange things in real-life stores!
  • Allow as many visits to the store as needed. Students forget things all the time!
  • Close the store at a certain time. I warn the class and then close the store after about 20 minutes. Then the teams have to make it work!
  • You don’t have to have fake money- but kids love it!
I hope I have convinced you to add a little twist and try a budget challenge. All of the resources in this post have that feature. The price lists and cost sheets are included in the resource and they are editable.