Some students taking the exam said they wanted to familiarize themselves with the HKDSE exam rundown, such as the use of student labels on answer sheets.

The mock exam, organized by Beijing Normal University-Hong Kong Baptist University United International College and local tutoring institution Beacon College, consisted of English, Chinese and mathematics - three of the core subjects under the SAR exam system.

Liberal studies is the fourth DSE core subject, to be renamed "citizenship and social development" in 2024 as part of an educational overhaul introducing units on patriotism and national development.

The mock exam's invigilation arrangements and marking schemes are consistent with the official exams conducted in Hong Kong, the organizers said.

A mainland DSE candidate, Zhang said they (mainland students) do not usually have the opportunity to experience examination procedures such as sticking candidate labels on their answer sheets instead of writing their name.

"These things are an extra source of pressure," he said. "But having experienced the mock exam, I think I won't be as nervous during the real thing."

Some Hong Kong students studying in Shenzhen will be taking the diploma next year, and have come to familiarize themselves, candidates said.

"I'm a bit nervous, because I've never sat for the exam in a new environment," a student, Yau said. "The mock exam is a good opportunity for us to try things out."

Last June, the Hong Kong Examinations and Assessment Authority announced that eligible schools in the mainland will be allowed to host and conduct DSE examinations starting in 2024.

However, students will have to take oral English, PE and music tests in Hong Kong.

Beacon College chairman June Leung Ho-ki said: "What are the strengths and weaknesses of candidates from a mainland background, and how about Hong Kong candidates? If we draw a comparison, we would be able to learn from each other."

Organizers said the next round of mocks will be held over the summer holidays, in Shenzhen as well as at the Zhuhai venue. It will also include electives in addition to the core subjects.

Beijing New Talent Academy, a school in Beijing is partnering with the HKEAA to offer DSE curriculum and become an examination venue.

The academy will start offering the DSE curriculum next month, with school and accommodation fees reaching up to 230,000 yuan (HK$267,000) for an academic year.

Founded in 1995, the private boarding school hopes to enroll 15 students in the 11th grade to start preparing for the DSE exams the following year and to become an official DSE venue.