3-5-ETS1-3: Testing and Improving a Prototype
Also called NGSS 3-5-ETS1-3 · Topic: Engineering Design · Engineering, Technology, and Applications of Science
The Official Wording
Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What 3-5-ETS1-3 Means in Plain English
Students in grades 3 to 5 test a model or prototype in a fair way to learn where it is weak. They change one thing at a time, repeat each trial, watch for the spot where it bends or breaks, and use what they find to improve the design.
Tests stay simple: one change, a clear measure such as how many books it holds, and repeated trials. This follows comparing solutions (3-5-ETS1-2) and leads to middle school testing that combines the best parts of several designs (MS-ETS1-3).
3-5-ETS1-3 I Can Statements
- I can plan a fair test that changes only one thing.
- I can find the place where a prototype fails.
- I can use test results to improve a design.
3-5-ETS1-3 Worked Example
A load test a class can run on a folded cardboard reading stand, using a stack of paperback books.
How many paperback books can our cardboard reading stand hold, and where does it give way?
Set It Up: Reading stands cut and folded from a corrugated cardboard box, ten matching paperback books, masking tape and a data table.
- Set the stand on the same table each time and add paperbacks one at a time.Same table, same books, one book per step
- Stop when the stand bends and note exactly where it failed.Trial 1: buckled as book 4 went on, at the back leg fold
- Build two more stands the same way and test each one.Trials 2 and 3: buckled at books 4 and 3, same fold
- Tape a cardboard triangle behind the back leg, changing nothing else.One change: the triangle brace
- Run three more trials with braced stands.Held 7, 7 and 8 books
The back leg fold was the weak spot every time, and bracing it more than doubled the load the stand could hold.
Why it works: A triangle cannot change shape without bending one of its sides, so the brace keeps the fold from collapsing and spreads the weight.
Common Mistakes with 3-5-ETS1-3
Changing several things at once
A braced stand made with thicker cardboard and new tape
Try this: Change one thing between versions, like adding the brace, so you know exactly which change made the stand stronger.
Ignoring where it broke
“It fell over, so it failed,” with no note about which part bent
Try this: Write down the exact spot that bent or tore first. That failure point tells you which part to strengthen next.
Testing just once
“The new stand held 8 books!” after a single try
Try this: Repeat each version at least three times. One lucky or unlucky trial can make a design look better or worse than it is.
Where 3-5-ETS1-3 Fits
Practice 3-5-ETS1-3
Quick Check
- Why change only one thing between versions of a prototype?
- What is a failure point?
- Why run each test three times?