✔ 最佳答案
It is way more complicated that you think.
1. When your son's one-way permit is approved, he will lose his Mainland residency immediately, which he will eventually lose his eligibility for NCEE.
2. Your son's education level may not meet the minimum requirement for university admission in Hong Kong.
So here is what you should do:
a. Make sure that he can take NCEE without issue;
b. Check with each individual universities for detail. For example, here is the information for City University of Hong Kong:
http://www6.cityu.edu.hk/meao/mainland/admission_method.htm