The spotlight has been placed on a curriculum authority after nine schools discovered they were teaching year 12 students the wrong topic days before final exams.
The Queensland Curriculum and Assessment Authority came under fire from the state government over the "extremely traumatic" mix-up impacting 140 ancient history pupils.
Education Minister John-Paul Langbroek put the authority on notice after launching an investigation into the bungle that was discovered on Monday, saying there had been "communication issues" in the past.
Brisbane State High School was the first to announce that their ancient history students had been studying the wrong Roman emperor ahead of Wednesday's final exam.
Mr Langbroek confirmed on Wednesday that overall nine schools across the state had been teaching pupils about Augustus Caesar when they were supposed to be studying Julius Caesar.
"I want to reassure those students and their parents and the teachers affected that we'll be making every investigation into how this happened," he said.
"Of course, I'm very unhappy at the situation developing ... for the stress that it will have caused for everyone."
The authority - which sets the topics for year 12 exams - would be the focus of the probe, Mr Langbroek warned.
The investigation will look at its guidelines and processes, with the minister noting there had been communication issues with schools during ex-Tropical Cyclone Alfred in March.
"I'll be making sure that the make-up of the Queensland Curriculum and Assessment Authority board is appropriately done for the future to make sure we don't see a repeat of these activities," Mr Langbroek said.
No other subject had been caught up in the bungle because ancient history had the only syllabus change this year, he said.
Augustus was a focus of the 2024 exam in Queensland, but this year the exam topic switched to Julius.
Students were told about the mix-up just days ahead of the final exam which is worth 25 per cent of their overall grade.
It is understood students could choose not to sit for Wednesday's exam, with measures in place to ensure a "fair" overall result for the subject.
The authority said schools were notified of the ancient history exam topic more than 12 months in advance.
For the 2025 exam, schools were first advised back in August 2023 and had been provided reminders since, Acting Chief Executive Officer Claude Jones said.
Special consideration will be applied to ensure a fair and accurate result for senior ancient history students, he said.
The authority said it would also work closely with the government to get to the bottom of the gaffe, taking steps to avoid a repeat in the meantime.
They include making the test topic more prominent on its websites, including it in the exam timetable published in May and seeking early confirmation that schools are teaching the correct subject.
"We are committed to ensuring this situation doesn't happen again," Mr Jones said.