Modern College says it is not responsible for 23 of its pupils being found guilty of plagiarism, and it has blamed the Examinations and Assessment Authority for not providing software to check the pupils' work.
The candidates enrolled with the private tutorial company had their marks in the Chinese-language section of this year's Diploma of Secondary Education exams invalidated after their school projects, which counted towards grades, were found to include plagiarised passages from the internet with no citations.
Without a score for the subject, they have lost any chance they might have had of getting into a university this year.
All the pupils, who sat the exam between March and May, were taught by the same teacher, but the school refused to disclose details of the teacher's experience and the branch of the school where they studied.
Modern College, a secondary day-school linked to Modern Education, has four campuses in the city.
The college's executive officer, Twinkle Lai Wai-ling, denied that the teacher involved had covered up for the pupils.
"Our teacher tried his or her best," she said, refusing to identify the person concerned.
"The teacher discovered three plagiarism cases and reported them to the authority. They are not sure about the other cases. It was the authority's responsibility to do further checks."
The projects were marked by the teacher and then sent to the exams authority.
The college also said it knew about the plagiarism cases in May and that it had held several meetings with the authority.
"The teacher's ability was limited and our resources were also limited," said college principal Kason Chan Kay-sang.
"The examinations and assessment authority didn't provide us with software to check students' work."
But the authority said it was not its responsibility to provide schools with anti-plagiarism software.
Chan said the college would strengthen the supervision of similar projects and that school principals might read pupils' work themselves in future.
The teacher involved has been suspended for violating the rules set by the authority and for not having asked the pupils involved to sign a declaration stating that their work was original and properly cited.
The head of the branch of the school has also been suspended.
Lawmaker Dr Kenneth Chan Ka-lok said he had written to Education Bureau Secretary Eddie Ng Hak-kim, urging the bureau to follow up on the case and to take appropriate action where necessary.
"I think it was a very serious case," Chan said.
"The teacher involved and Modern College itself might have covered up for the cheating pupils.
"The teacher and the college had the ability and the responsibility to prevent this happening, but they didn't fulfil their responsibilities," he said.