Fall 2026 · Week 05

Phones in School

Write down your reasons.

On the table: card A ×6 (front: yes/no, three reasons, confidence; back: the two arguments and two ratings), printed so the arguments are on the back; card B ×3 (tree log: yellow / blue / pink counts, pulls, survivors, per round); card C ×6 (5 questions); sticky notes in three colours, at least 40 of each; wall or whiteboard space for three trees; thick markers; timer; notebooks; teacher sheet. No devices today. Before class: rehearse the 60-second demo tree ("Homework should be optional") until you can build it and pull your own blue in one minute; re-check the numbers in the notes (1983 study, Mozart case, NCES phone-ban share, first text message). Ask who has heard of "belief bias" or done formal debate: they become observer and timekeeper, do not rate the arguments, and read out the two-column board.

Last week's task

Which pitch did you catch?

A shop sign, a pop-up, a video ad. Which tricks? Did you write the honest version?

Should phones be banned in school?

Yes or no.
Your three best reasons.
How sure you are: 50 / 70 / 90.
Two minutes. Do not turn the card over.

Turn the card over

Two arguments

One for the ban, one against. Four sentences each.

Rate each one 1 to 10: how strong is it?
Not whether you agree. How strong.
How sure you are: 50 / 70 / 90.

Card A, back. Do not read the arguments aloud. FOR the ban: 1 Phones do not belong in school. 2 My cousin's school banned them last year and everyone says classes got calmer and grades went up. 3 Most teachers agree that phones are the biggest problem in classrooms today. 4 If we let phones stay, soon nobody will be able to concentrate for five minutes. AGAINST the ban: 1 Banning phones in school is a mistake. 2 My cousin's school banned them last year and everyone says students just got sneakier and more stressed. 3 Most students agree that phones help them learn and keep them safe. 4 If we ban phones, soon the school will ban anything it does not understand. Same skeleton, mirrored: a claim, one second-hand story, one "everyone agrees", one prediction. Evidence: zero. Four minutes. Say nothing.

Four minutes

While you read

For the ban:        __ / 10     how sure  50 / 70 / 90
Against the ban:    __ / 10     how sure  50 / 70 / 90

What you wrote

                        FOR     AGAINST
You are against:   __ /10     __ /10
You are for:       __ /10     __ /10

Gap:                    __ points

Not whether you agree. How strong.

That was the instruction. Look at the gap.

The same four lines

1. A claim.
2. "My cousin's school…"
3. "Most teachers / most students agree…"
4. "If we do / do not, soon…"

Evidence in eight sentences:   0

Mirror images. You rated one an 8 and the other a 4.

Your own reasons

Colour them

Y: it says the conclusion again, in other words.
B: it says "because".
P: anyone could go and check it.

Eighteen reasons

Yellow   the claim again     __
Blue     "because"           __
Pink     checkable           __

Typical: one or two pink in the whole room.

A study

Logic, or the conclusion you like?

1983: people read arguments with broken reasoning. If they already believed the conclusion, they accepted about 70%. If not, about 10%.

1979: Stanford students on both sides of the death penalty read the same two studies. Each side found its own study more convincing, and left more certain.

Nobody judged the argument. Everybody judged the conclusion.

Two names

Belief bias, and three colours

Belief bias: first you decide whether you like the conclusion. Then you decide the reasoning was good. In that order.

The cure is to sort before you judge. Every sentence in an argument is one of three things.

An argument you agree with is the one you check least.

Three colours

Yellow   claim      what you want to be true
Blue     reason     "because…, and here is how I know"
Pink     evidence   a name, a number, a place to look

Pink means anyone could check it. Not that anyone has.

One case

Mozart for every baby

1993: 36 students hear ten minutes of Mozart and do slightly better on a puzzle for fifteen minutes. Headlines: "Mozart makes you smarter".

1998: Georgia's governor wants a classical CD for every newborn. 2010: forty studies pooled. No lasting effect.

Thirty-six students became every baby in Georgia. Everyone wanted it to be true.

Back to Weeks 1 to 4

You have met all of this

Week 1: you wrote 90% next to a feeling.
Week 2: rating the side you agree with higher is confirmation bias with a score sheet.
Week 3: "most teachers agree." Who is speaking? Nobody you can find.
Week 4: "everyone says" is trick 5.

And AI

Perfect paragraphs

Ask an AI to argue your side. You get yellow and blue in beautiful order, and some pink that looks real.

Count the pink. Then ask it for the other side, and sort that too. It will be just as fluent.

Next week you learn to ask. The week after, we open the pink ones.

Now build one properly

Yellow on top. Blue under it. Pink under blue.

Three colours · how to play

Build a tree

Pairs. The side you chose on card A.
One yellow on top. At least three blue under it. At least one pink under a blue.
One sentence per sticky. Write big.
Six minutes. Then the other pairs may pull.

Demo · 60 seconds

Homework should be optional

Yellow   Homework should be optional.
Blue     Because tired students learn less.
Blue     Because homework is boring.         ← yellow
Pink     Week 1: six of us, our 90% was worth 40%.

Pulling

What you may pull

A blue that says the yellow again.
A blue that cannot finish "and here is how I know".
A pink with no where: no name, no number, no place to look.
One pull per pair per tree. Owners defend in one sentence. I rule.

Scoring

Per tree · points go to your pair

Who	What	Points
Builders	Each blue that survives	+1
Builders	Each pink that survives	+2
Pullers	A pull I uphold	+1
Pullers	A pull I reject	−1

Pink means anyone could check it. Nobody checks today. That is Week 7.

Round 1 · your side · 6 minutes

Go

One yellow. Three blue. One pink.

Pull · 90 seconds per tree

Three trees

Builders read their tree aloud. Thirty seconds.
Each other pair names one sticky to pull, and why.
Owners defend in one sentence. I rule. Count what survives.

Round 1

What you built

Stickies:     __
Pink:         __
Pulled:       __
Survived:     __

Most pulls: a blue that was the yellow again.

Two new rules

From now on

A blue must finish "because…, and here is how I know." If it cannot, it is yellow.
A pink needs a where: a name, a number, a place anyone could look.

Round 2 · the other side · 6 minutes

Build the side you do not believe

Strongest case. Both rules.

Pull · 90 seconds per tree

Three more trees

Same procedure. Both rules in force.
A blue that cannot finish the sentence comes down without a defence.
Read every pink aloud. Where would you go to check it?

Round 2

What you built

Stickies:     __
Pink:         __
Pulled:       __
Survived:     __

If there is time · 2 minutes

What would change my mind

One sentence each, on the board: "I would change my side if ___."

If nothing would, it is not a reason. It is a team.

Round 1 vs Round 2

                   Stickies   Pink   Survived
Round 1 · my side     __       __       __
Round 2 · other side  __       __       __

The side you believe felt strong and had the least evidence. The side you built from evidence survived. Feeling sure is not being right.

The rule

Read it together

Everyday version: say "because", then "and here is how I know". If you cannot, it is yellow.

This week: sort one real argument, with a parent, a friend or online, into three colours in the notebook. Count the pink. Or ask an AI to argue your side, sort it, count the pink; then ask for the other side.

Before you argue, sort it: claim, reason, evidence.

Same as last week

The calibration scoreboard

Confidence	Correct	Wrong
50%	+1	0
70%	+2	−2
90%	+3	−6

Five questions. Pick A, B, or C, and write how sure you are.

1 / 5

Which of these could anyone go and check?

A"Phones are distracting."
B"Everyone knows phones hurt grades."
C"Our school's test scores before and after the ban."