Plant errors in a worked example so students can hunt them

Plant errors in a worked example so students can hunt them

Students often learn more from finding a planted error than from another clean worked example. The bit teachers skip is that writing a plausibly flawed example, the kind a student at this year level would actually produce, is harder than writing the correct one.

The prompt

You are an experienced [SUBJECT] teacher in an Australian [PRIMARY / SECONDARY / TERTIARY] classroom. You have marked enough student work in this year level to know what mistakes are real and what mistakes a teacher would invent.

Concept I am teaching: [CONCEPT IN ONE PLAIN SENTENCE]
Year level: [YEAR LEVEL]
Curriculum link: [ACARA v9.0 content descriptor, VCE study design dot point, or your own success criteria, copied verbatim]
What students have done so far on this concept: [ONE OR TWO SENTENCES, e.g. "Two lessons on solving two-step linear equations. Students have practised on paper and mini whiteboards. They have not yet seen variables on both sides."]

Produce ONE worked example on this concept that contains [NUMBER, default 3] planted errors a real student at this year level would plausibly make. Not typos. Not random arithmetic slips. Specific misconceptions.

Format:
1. Write the worked example as a student would write it. Student voice, all working shown, no teacher narration in the body. It must look like real student work, not a teacher's annotated example.
2. Each planted error must:
   a. Be subtle enough that a student holding the misconception would not notice it.
   b. Map to a specific, named misconception, not a typo.
   c. Not invalidate the whole example. A student should be able to find error 2 after fixing error 1, and error 3 after fixing error 2.
3. The three errors should be roughly equal in difficulty to spot. Do not give me one obvious error and two hard ones, because that lets the class "win" early and stop hunting.

Then, in a separate "Answer key (teacher only)" block, list:
- Each error: the line it appears on, exactly what was written, what the correct move was, and the misconception that produced it (named in plain English, not "computation error").
- One short follow-up question per error I could ask a student who missed it.

Then, in a separate "How to run it" block, give me three options:
- Solo (5 minutes): students hunt alone, then compare with a partner.
- Paired (10 minutes): students hunt in pairs, each pair must agree before declaring an error.
- Whole class (15 minutes): example under a visualiser, students vote line by line. One scribe per group.

Finally, "Sanity check": one sentence on the most likely way this activity goes wrong, and one small change I could make to reduce that risk.

Australian English throughout. Do not use the phrases "deep dive", "unpack", or "scaffold their thinking".

What it does well

Forces the model to commit to named misconceptions for each planted error, which is the move that turns "find the mistake" into a diagnostic activity instead of a proof-reading drill. The "roughly equal difficulty" line is the one that stops the model defaulting to one obvious error and two genuinely hard ones, which is the failure mode that wrecks the activity in the room.

Where it falls over

The model is reading the concept cold, so the worked example will sometimes contain a planted error that is not actually a misconception your students hold. Always check the answer key against your own marking memory before you print. The prompt also cannot judge whether your class is ready for this. If they have not yet grasped the underlying method, hunting errors will quietly reinforce them.

Try it like this

For Year 8 maths (two-step linear equations): ask for the three errors at distinct stages of the working: one in the rearrangement, one in the inverse operation, one in the final check. Stick it under a visualiser and have one student be the scribe who corrects the line as the class votes.

For Year 10 English (analytical paragraph on a set text): the worked example becomes a planted paragraph with three errors. Likely candidates: a topic sentence that does not take a position, a piece of evidence that does not match the claim, and a concluding sentence that introduces a new argument. Students annotate before they rewrite.

If you only have ten minutes today, run it on the lesson where you usually open with a "do now" retrieval question. Replace the do-now with a planted-error example on the same skill. Retrieval and diagnostic happen in the same five minutes.

The clean worked example shows students what good looks like. The planted one shows them what they were about to do.