Thinking Routines / 3-2-1 Bridge
3-2-1 Bridge
Three words, two questions and one analogy, collected before you teach a topic, then again at the end. The gap between the two columns is the lesson.
Opens on the whiteboard to model with the class · free to start · printing is optional
The sheet it prints (optional)
What is the 3-2-1 Bridge thinking routine?
3-2-1 Bridge is a Project Zero thinking routine where a class gives three words, two questions and one analogy about a topic before teaching it, then again at the end, and explains what changed.
The analogy is a simile or metaphor. The explanation of what changed is the bridge. IB PYP and MYP schools use it a lot.
How do you do 3-2-1 Bridge, step by step?
3-2-1 Bridge runs once per unit, in two halves: about ten minutes before you teach and fifteen at the end.
- Name the topic before any teaching (1 minute).
- Three words, written alone (2 minutes).
- Two questions they want answered (2 minutes).
- One simile or metaphor. Start it for them: 'Rivers are like...' (3 minutes).
- Put it away and teach the unit.
- Answer again, cold. Same prompts, no looking back (5 minutes).
- Build the bridge. Compare the two in pairs, then write what changed and what changed it (10 minutes).
3-2-1 Bridge examples by subject and age
Five 3-2-1 Bridge examples: a class's first response, what changed, and their bridge.
| Before | After | The bridge |
|---|---|---|
| RE: Diwali, Year 3 (grade 2) | ||
| Lights, fireworks, sweets. Who celebrates it? Why the lamps? Like Bonfire Night. | Rama, Sita, Lakshmi. Like New Year and a welcome home. | We thought it was fireworks. The lamps light Rama's way home. |
| Science: electricity, Year 4 (grade 3) | ||
| Plug, shock, bulb. Where does it come from? Why does it hurt? Like magic in the wall. | Circuit, battery, switch. Like a running track with no gaps. | It needs a full loop, which is why a switch can stop it. |
| History: the Vikings, Year 5 (grade 4) | ||
| Horns, raiders, longships. Why did they come? Were they all fighters? Like pirates. | Traders, farmers, settlers. Like a travelling market that sometimes turned violent. | Most Vikings farmed and traded, so 'pirates' only fits the raids. |
| Computing: the internet, Year 6 (grade 5) | ||
| Wi-Fi, Google, games. Where is it kept? Who owns it? Like a cloud over the house. | Servers, cables, packets. Like a postal service that cuts your letter into pieces. | We thought it floated in the air. It runs through cables under the sea. |
| Geography: rivers, Year 7 (grade 6) | ||
| Water, fish, flow. Where does it start? Why do they flood? Like a road for water. | Source, meander, erosion. Like a sculptor that never stops cutting. | It shapes the land, so the road became a sculptor. |
How do you run 3-2-1 Bridge on the whiteboard?
3-2-1 Bridge on the Sage board runs in three steps: first response, new response, then the bridge.
- The first response is hidden. Press Next and it is covered while the class answers again. Show first response brings it back.
- It waits for you. The board keeps everything on that classroom computer, typed or in pen. Open the page weeks later and it says Carried on from last time.
- The bridge builds itself plank by plank between the two columns.
- Type or write. The keyboard button swaps typing for the pen on the interactive whiteboard (smart board).
Is there a printable 3-2-1 Bridge template?
Yes, the 3-2-1 Bridge sheet is an A4 fold-over, free to try. Pupils (students) fill the top half, then fold it back along the dashed line so they can't copy it. The bottom half takes the new response and the bridge.
Should pupils look back at their first response?
No, pupils should not see their first 3-2-1 Bridge response until the second one is written. A child who can see it writes towards it or away from it, and the comparison means nothing.
What age is 3-2-1 Bridge for?
3-2-1 Bridge works from Year 3 (grade 2) into secondary (middle school). Years 1 and 2 (kindergarten and grade 1) find analogies hard, so drop to 3-2.
| Year group | US grade | What to change | How long |
|---|---|---|---|
| Years 3–4 | Grades 2–3 | Three words and two questions. Analogy optional. | 10 min each half |
| Years 5–6 | Grades 4–5 | All three. Insist the analogy is explained. | 15 min each half |
| Year 7 and up | Grade 6+ | Add: which of your first questions never got answered? | 20 min each half |
How do you assess a 3-2-1 Bridge?
Assess a 3-2-1 Bridge by comparing the two similes first, then the questions, then the words. A new simile means the child now thinks the topic is a different kind of thing. A first question that never got answered is your next lesson.
What usually goes wrong?
The most common 3-2-1 Bridge mistake is forgetting the first half, because it has to happen before any teaching. Plan it into lesson one.
- The two responses look the same. That is a finding, not a failure. Ask them to explain one word they used both times. The explanation usually changed even when the word didn't.
- The analogy gets skipped because it takes longest. It is also the most useful bit.
- The bridge says 'I learned more'. Ask which lesson or fact changed their mind.
3-2-1 Bridge vs KWL, I Used to Think and the 3-2-1 exit ticket
3-2-1 Bridge is the only one of these that asks the same prompts at both ends of a unit, then asks what changed.
- KWL (know, want to know, learned) has a before, but no second go at the same prompts.
- I Used to Think, Now I Think keeps one free answer from the start and sets one beside it at the end, with no fixed prompts to compare.
- The 3-2-1 exit ticket is a different thing: three things learned, two facts, one question, at the end of one lesson.
Free to try. Running it uses one token, printing included. Every account gets 20 free tokens, and Pro gives 50 a day.
Where this routine comes from: the 3-2-1 Bridge thinking routine was developed by Project Zero, a research center at the Harvard Graduate School of Education. Sage Teachers is not affiliated with, endorsed by, or connected to Harvard University or Project Zero. The prompts and the wording on this page are our own.