Why is that?

Because children who want to take the DSE exam or the Hong Kong, Macau, and Taiwan Overseas Chinese Student Joint Examination to apply for mainland universities need to meet the conditions for obtaining Hong Kong permanent residency. It takes at least 7 years from obtaining a Hong Kong resident ID card to finally getting permanent residency. For families who are determined to apply for mainland universities, the latest time to plan for Hong Kong residency should be when the child is 9 years old. After a year of application and approval, they can obtain Hong Kong residency at the age of 10 and permanent residency at 17, allowing them to participate in the Overseas Chinese Student Joint Examination. At that time, a score of 400 would be sufficient to enroll in top mainland universities like 985 and 211, which undoubtedly poses a significant challenge for the more than 1,000 candidates in mainland China who are currently in fierce competition.