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The fairest check needs no software: ask students to explain and extend their own work. That tests what you care about, whether they understand what they handed in.
Why not just use an AI detector?
Because detectors make mistakes, and the mistakes land on honest students. In a 2023 study in the journal Patterns, seven popular GPT detectors labelled more than half of 91 TOEFL essays by non-native English speakers as AI-generated, with an average false-positive rate of 61.3%. The same detectors classified essays by US eighth-grade students accurately. If many of your students write in their second or third language, as many do in Indian classrooms, that bias matters.
A separate test of 12 public tools and two commercial systems, published in the International Journal for Educational Integrity, concluded that the tools were “neither accurate nor reliable”, and that disguising the text made them worse. We explain why the scores misfire in why AI-writing detectors get it wrong.
What should your AI rule say before the work is set?
Students cannot follow a rule they have to guess. When you set an assignment, say which of three levels it is:
No AI: the work is done without AI tools, often in class.
AI for help, not answers: students may ask AI to explain a concept or check a step, and must note what they used it for.
AI allowed: students may use AI freely, but must be able to explain everything they submit.
Add one line that applies at every level: “Anything you hand in, you may be asked to explain in person.” Said at the start of term, it makes a viva a normal part of the course rather than an accusation. For where help ends and copying begins, see our guide to AI and homework honesty.
How do you run a two-minute viva follow-up?
Pick one step from the student's own work and ask about it, curiously. Ask several students, not only the one you doubt, so nobody feels singled out.
Here is a sample for a Class 11 projectile problem:
Teacher: “In Q2 you wrote that the time to reach the top is u sin θ / g. Where does that come from?”
Student: “At the top the vertical velocity is zero, so I used v = u + at with v = 0 and a = −g.”
Teacher: “Good. If the launch angle went from 30° to 60° at the same speed, would the range change?”
Student: “It stays the same, because sin 2θ is the same for both angles.”
Teacher: “Then which ball stays in the air longer?”
A student who did the work usually answers in their own words, even roughly. One who copied often repeats the written text or cannot say why a step is there. Neither is proof: nervous students freeze, and fluent ones rehearse. Treat answers as one piece of evidence.
Can drafts and version history show how work was made?
Often, yes. Work written over days leaves a trail: notes, crossed-out attempts, a changing draft. Ask for the trail with the final version.
For typed work in Google Docs, the version history panel, opened from “Last edit” at the top right, shows earlier versions and what changed.
For handwritten maths and physics, ask for a photo of the rough sheet, mistakes included.
For longer projects, hold two short check-ins before the deadline.
Some students really do write in one sitting, or type up a paper draft once. A missing history is a reason to talk, not a verdict.
What is an in-class extension task?
It is a short task, done in class, that builds directly on the homework. If the homework was the projectile problem, the extension might be: “Same ball, same speed, now thrown from the edge of a 20 m cliff. Find the new time of flight.” Give it ten minutes.
A student who understood the homework can usually adapt it. If the take-home answer was perfect and the extension is blank, you have a specific, fair reason to talk.
What should you do if the answers don't match?
Start with a private conversation, not a charge. One opening that works: “Your homework uses a method you couldn't use today. Walk me through how you made it.” Then listen. Follow your school's academic-integrity policy for the next step, and give the student a way to show the learning again, such as a redo followed by a short viva.
For students, the lesson is simple: use AI to understand, then make sure you can do the problem without it, using these five quick ways to check you understood an AI explanation. Fermi's AI tutor is built to teach rather than just answer: it decides whether to explain, ask or show, and checks understanding as it goes, so you get practice explaining your own reasoning.
