PRIMM and pair programming

Why it matters

Many beginner programming lessons jump straight to "write a program that...". For novices this is like asking someone to write an essay in a language they have only heard spoken. They stare at a blank editor, copy something from the internet, or give up. Two well-researched approaches give students a gentler, more structured path: PRIMM for lesson structure and pair programming for collaboration.

PRIMM: read before you write

PRIMM was developed by Sue Sentance and colleagues in England. It moves students from reading code to writing it in five stages:

The key idea is that reading and understanding code comes before writing it. Students get a working example to reason about, so their first experience is success, not a blank screen. The approach also gives you natural checkpoints: if many predictions are wrong, you stay longer on Investigate.

Worked example: a PRIMM lesson on for loops

Predict:

total = 0
for n in range(1, 4):
    total = total + n
print(total)

"What will this print? Write your answer before running it." Common predictions: 6 (correct), 10 (thinking range includes 4), or 3 (thinking the loop runs once).

Run: students run it and compare. Discuss why range(1, 4) gives 1, 2, 3.

Investigate:

1. Add a print(n, total) inside the loop. What do you see?
2. What would range(1, 6) print? Predict, then check.
3. What happens if total = 0 is moved inside the loop? Why?

Modify: make it add only even numbers from 2 to 10.

Make: write a program that multiplies the numbers 1 to 5 (5 factorial), then an extension: ask the user for n.

Pair programming: two people, one problem

In pair programming, two students work on one computer:

• The driver types and focuses on the current line.
• The navigator reads, checks, thinks ahead and suggests.
• They swap roles regularly, often every 5-10 minutes, with a timer.

Studies in university and school settings have linked pair programming with better completion rates, more confidence and better retention, including for students under-represented in computing. It also reduces the number of "I'm stuck" hands, because pairs solve many problems themselves.

Making pairing work

Pairing fails when one student does everything. Structure helps:

• Role cards on the desk describing what each role does and says.
• A visible timer and a clear signal to swap.
• Talk norms: the navigator suggests, does not grab the keyboard; the driver explains what they are typing.
• Thoughtful pairing: pair students of similar confidence where possible, and change pairs between units.
• Individual accountability: short individual exit questions so you can still see what each student understands.

PRIMM and pairing combine well: pairs predict and investigate together, then each student does a short individual Make task.

Common mistakes

• Skipping Predict. Running code first removes the moment where misconceptions show.
• Investigate questions that only ask "what does it print?" Ask "why?" and "what if?" too.
• Unstructured pairs. Without roles and swaps, the more confident student drives the whole time.
• No individual check. Pairs can hide a student who has not understood.

Quick recap

• PRIMM = Predict, Run, Investigate, Modify, Make: read and reason about code before writing it.
• Predictions surface misconceptions; Investigate questions deepen understanding.
• Pair programming uses driver and navigator roles with regular swaps.
• Structure pairing with role cards, timers and individual exit checks.

Try it

Open the Do tab and plan a 50-minute PRIMM lesson that uses pair programming.