Mazenod College in Melbourne’s outer east has found nearly a quarter of its Year 12 students used artificial intelligence to cheat on a key English oral exam, and the school has already cut the marks of those involved.

The issue surfaced after oral assessments submitted two weeks earlier aroused suspicion among teachers, prompting a review of the Year 12 English oral exam process. Up to 50 boys were caught, making this one of the clearest signs yet of how quickly AI can slip into school assessment when students are asked to present their own thinking out loud.

Paul Shannon said on Tuesday that the affected students had been spoken to and given the appropriate reduction in marks for the assessment. He said the review had found evidence that suggested artificial intelligence tools were used by several students, and added that AI had no place in assessments and examinations where every student must demonstrate knowledge independently and fairly.

The assessment was designed to measure students’ understanding of the subject and their independent thinking, which is why the findings matter beyond one classroom. Mazenod College is a Catholic school in Mulgrave, and the case lands at a time when schools are trying to decide how to protect oral and written work from tools that can now produce polished answers in seconds.

Even so, the college said it did not believe the cheating had been coordinated among the students, despite the fact that almost a quarter of the Year 12 cohort was caught. That leaves the harder question unanswered: whether this was a set of isolated decisions, or a sign that enough boys in one year level were willing to use the same shortcut without needing to plan it together.

The Victorian Curriculum and Assessment Authority has said disallowed or unattributed use of AI may breach academic integrity, but it also says it is up to each school to investigate misuse. Andrew Smith said teachers are often the best AI detectors because they know their students and can interrogate their work, and that the authority wants to keep a balance between teachers’ judgment and independent assessment. He said the VCAA will keep talking to teachers and monitoring whether adjustments are needed.

For Mazenod College, the immediate punishment is done. What remains is the larger test for schools across Victoria: how to spot AI use before an assessment is marked, and how to keep exams credible when the tools students carry in their pockets can imitate the very thinking schools are trying to measure.