Complete source
Ordinary fictional storeroom plan. Two labelled rock-display silhouettes, S and T, lie beside a printed centimetre scale. S spans 0–4 cm and T spans 0–6 cm on the supplied diagram. The plan asks, “Which labelled silhouette has the longer base in this drawing?” The same scale, left-edge zero convention and base direction are used. A sealed display cannot be scratched or opened. The supplied readings are retrospective: they are not children's prior predictions or measurements of actual rocks. A separate optional classroom job uses two large plain paper rectangles, chosen by the adult, to practise a real ruler procedure.
Day
46
Evidence
Question/prediction/procedure/outcome chronology; correct diagram units. Actual I03 instrument-use evidence requires actual child operation/reading, not a click or supplied-number copy.
Moves
- Invite, 3 minutes: choose the drawing-reading job or actual plain-paper measuring job. Explain that the two jobs make different evidence.
- Read and question, 5 minutes: read the complete plan. Locate the exact base feature and unit. Ask children what the question is before they read the numbers; the supplied diagram is never described as an unseen future result.
- Model, 5 minutes: align zero with a paper edge using a familiar ruler; describe endpoint and centimetre interval. For diagram work point to the printed 0–4 and 0–6 spans without calling that real-rock instrument use.
- Plan together, 6 minutes: for actual paper work write question, visible-clue prediction, procedure, matched ruler/orientation, and a safe stop. The child states a prediction before measuring; an adult-operated ruler is recorded as adult operation.
- Do and record, 12 minutes: follow one route. Make a small table labelled Source and unit. In actual paper work keep every reading as obtained, including uncertain alignment; never replace it with the fictional diagram result.
- Return, 5 minutes: explain one comparison and a boundary. Ask whether a different base direction or scale would still answer the same question. Keep plans and outcomes distinct.
Next teaching
For tick-counting, offer C11's interval walk. For a comparison without a boundary, offer C12's drawn-package question. Real measurement practice can be repeated with a different paper pair without altering the held source.
Ordinary staff model
Possible ordinary reading: “T is 6 cm and S is 4 cm on this diagram, so T's drawn base is longer by 2 cm. This doesn't tell me hardness or the size of a real rock.” Before a new actual paper comparison, a child can predict from visible bases, then record the result separately after using a familiar ruler.
Question
How can we compare a visible feature without secretly changing the question?
Routes
Complete instruction
Use the full fictional drawing description and record S and T's supplied base spans in a two-row cm table. Make a comparison for the drawing only. If printed at another size, the supplied labels still describe the drawing record; do not infer real dimensions from page size.
Id
D46-1
Title
Scale reader
Complete instruction
On an adult-approved clear desk use two large paper rectangles and a familiar centimetre ruler. Say or record a visible-clue prediction before measuring. Align zero, read the base endpoint and record actual readings with the helper's role. Compare only this feature of these paper pieces; no rock test is implied.
Id
D46-2
Title
Ruler crew
Complete instruction
In Desk or paper use Next question and Evidence/boundary to keep a proposed paper comparison distinct from any supplied record. Enter actual readings only if obtained; choose Source view to keep diagram and actual-paper provenance separate. Preview does not produce a measurement.
Id
D46-3
Title
Question-first Desk
Title
Ask first, record afterwards