The expedition’s shrinking memory

Year 6 · 70 minutes · Context

Driving question

What happens when the fact you need falls out of view?

Conceptual explanation

A system can only use information available to its current computation. This context simulator keeps a limited suffix of a fictional expedition log. A deterministic answer rule extracts a fact only if its complete sentence is visible. Increasing the window can restore a fact, but it does not resolve contradictions or ensure a real language model will use it correctly. The lab performs text slicing and rule-based extraction, not LLM inference.

Learning intentions

Success criteria

Vocabulary

Teacher preparation

Print the fictional log on a long strip. Cover its beginning with paper to leave only the last words visible. Mark that the lab counts whitespace-separated words, unlike production tokenisers.

Materials

Prerequisites and grouping

Identify a fact and a condition in a short instruction. Useful earlier investigations: y6-tokens Use pairs with predictor/operator roles. Swap after the first comparison. Each learner draws or writes their own explanation using one exact case.

Curriculum connections

Australian Curriculum Version 9 · Digital Technologies: AC9TDI6P04, AC9TDI6P06. Selected aspects only. This activity contributes evidence; it does not cover the full descriptor or achievement standard. A programming descriptor is not claimed for merely moving controls. ACARA AI curriculum connection · V9 Technologies These are planning connections, not ACARA endorsement or exhaustive descriptor alignment.

Timed teaching sequence

0–9 min · Read a partial log

Ask for the camp opening time from a covered strip.

Ask: “Can you answer from the words you can actually see?”

Listen for: “No; the time sentence is covered.”

9–17 min · Predict the boundary

Predict the minimum window that contains the complete fact sentence.

Ask: “Is half the sentence enough to support the answer?”

Listen for: “It may leave out the important condition.”

17–38 min · Slide the window

Change the word budget and inspect included/excluded text and extraction result. Keep the log and question fixed.

Ask: “Which exact words returned when the answer became available?”

Listen for: “The sentence containing the opening time.”

38–46 min · Add a conflicting update

Use the contradiction edge case with two visible times and dates.

Ask: “Did a larger window solve the disagreement by itself?”

Listen for: “No; we need to interpret which update applies.”

46–64 min · Redesign the briefing

Write a concise, dated summary from supplied facts and place essential information near the query. Preserve conditions and mark unresolved conflicts.

Ask: “What could a too-short summary accidentally remove?”

Listen for: “The date or exception that makes the fact accurate.”

64–70 min · Document the limit

Collect window size, visible evidence and a reasoned unknown response.

Ask: “Does visible information guarantee correct use by an LLM?”

Listen for: “No, availability is only one requirement.”

Misconception to surface

A generator remembers everything.

Prediction

Reduce the context budget with text and question fixed. Predict when the complete supporting sentence disappears.

Counterexample

A larger window can include conflicting updates, so more context does not automatically settle which fact applies.

Redesign challenge

Create a concise dated briefing preserving the required fact, qualifier and any unresolved contradiction.

Discussion and reflection

Formative assessment

Ask learners to quote the actually visible supporting sentence rather than a remembered hidden sentence. Check that summaries retain dates and conditions.

Differentiation

Use a six-sentence paper log and count words together. Allow highlighting rather than lengthy written explanation.

Extension

Compare suffix truncation with a relevance-based selection strategy and test which question each loses.

Final artefact

A context-budget briefing with a highlighted evidence sentence and a conflict note.

Safety and data boundaries

Use only the supplied fictional log. Never paste private school correspondence or student records into the journal.

Hardware investigation

Evaluate complete-fact availability at thousands of synthetic positions and twenty context budgets. Change fact length to reveal boundary failures; availability alone does not establish correct model use.

Lesson-specific rubric

Criterion Beginning Secure Extending
Context reasoning Assumes all past text is available Identifies included and excluded evidence Explains complete-sentence and contradiction limits
Briefing design Copies an unsupported answer Preserves the fact within budget Keeps qualifiers and explicitly handles conflict

Curriculum and assessed evidence

Australian Curriculum Version 9 · Digital Technologies

References: AC9TDI6P04, AC9TDI6P06. Read the current source (checked 2026-09-07).

Evidence to assess: A context-budget briefing with a highlighted evidence sentence and a conflict note.

Selected aspects only. This activity contributes evidence; it does not cover the full descriptor or achievement standard. A programming descriptor is not claimed for merely moving controls. Moderate the supplied illustrative responses against your school unit and current achievement standard.

Choose a teaching schedule

These are planning estimates to test with your class. A short session develops one supported claim; it does not compress the whole senior project.

Stage 45 minute focus 60 minute investigation
Readiness and prediction 0–5 0–5
Trace the supplied example 5–13 5–15
Author and run cases 13–25 15–35
Counterexample and redesign 25–35 35–45
Explain and discuss 35–42 45–55
Export and handover 42–45 55–60

For a longer project, use three 50-minute sessions. Session 1 (0–50): readiness, model, hypothesis and initial cases. Export a project and record the next test. Session 2 (50–100): reopen, check settings, author counterexamples and revise the design. Export the changed project and identify unresolved evidence. Session 3 (100–150): independent peer test, final artefact, individual explanation and moderation. If using two 60-minute sessions, stop at minute 60 after saving the first comparison; use 60–120 for redesign, independent test and defence.

Readiness and access

Entry check: Identify a fact and a condition in a short instruction. Ask the learner to demonstrate it before choosing the level of support.

Preparation: allow about 15 minutes to run the starter, print the cards and check a project can be reopened. This estimate has not yet been measured in a classroom pilot.

Read the entry question aloud, model one row, and label the units. Offer the case table as a large-print sheet. Keep mathematical derivations optional until the learner can explain the comparison.

For one device, use a projector: one pair predicts, one operates, and the class records on paper. Swap roles after the first comparison. For individual access, support keyboard controls and a written table equivalent to each visual. Learners may explain orally or with an annotated diagram. Never require personal data, a recorded voice, or a photograph.

Mixed readiness: if the entry check is difficult, use the linked prerequisite and the first two case cards; retain the same central question. If secure, ask the learner to design an unseen test and state which explanation it could disprove.

Supplied experiment and answer notes

Keep complete lines from the beginning until the budget is exhausted. Report whether declared essential lines survived.

Starting parameters: Word budget = 15

0 essential conditions lost; 0 words remain.

line words kept essential essential lost
The walk leaves at nine. 5 True False False
When it rains the walk is cancelled. 7 True True False
Bring a water bottle. 4 False False False
The guide wears a green hat. 6 False False False

Illustrative responses and marking notes

These are authored examples, not work collected from children. Assess reasoning using the lesson rubric, not whether the first prediction was correct.

Beginning: “It worked because the result looks right.” This identifies no exact case, control or measurement. Ask the learner to point to one row and say what happened.

Developing: “In the first case I recorded line: The walk leaves at nine.; words: 5; kept: True; essential: False; essential lost: False.” This cites evidence, but does not yet explain how the result follows from the rule. Ask the learner to trace the relevant step.

Secure: “For the first supplied case, line: The walk leaves at nine.; words: 5; kept: True; essential: False; essential lost: False. I can trace it using this mechanism: Keep complete lines from the beginning until the budget is exhausted. Report whether declared essential lines survived. My result supports a claim about these supplied cases. It does not establish that the same result holds outside them.” Look for an accurate trace, the actual settings and a bounded claim; accept equivalent oral or visual evidence.

Extending: The learner constructs and reruns a new case, reports whether the first explanation survives, and defends a revised design. Use this concrete challenge: Write your own six-line briefing. Preserve a condition under a word budget and test the resulting answer. Require the original and changed evidence and this boundary: Presence does not prove a model will use a condition correctly. Test the resulting briefing separately.

Moderation: first assess independently against each lesson criterion. Compare the exact trace or artefact that led to your judgement. Resolve differences using evidence, not polished language. Keep each learner's individual explanation even when the artefact was produced in a group.