I think it is unfair to simply compare the grades of the US system with that of the Hong Kong system. The whole approach to schooling is quite different in the two places.
The US system is an inclusive system where they are trying to get everyone to pass at the grade level. This means that very few children fail. It is also a very board system where many subjects are taught to a lower level. The Canadian system is also similar to the US system.
The Hong Kong system is based on the old English system. This is not an inclusive system and the marking is such that it is separating the children who will benefit for more academic learning and those who would be suited to more practical learning. Thus only about half the children are expected to pass the GSCE exams. The English system also specializes much earlier than the US system.
For example, My elder daughter graduated from the Canadian School. In her last two years at school she took 15 subjects which included English, Chinese, Maths, Technology, History, Science and Drama. She was still learning a wide variety of subjects and expected to be able to good at all of them.
My elder son has just started boarding school in England and will be taking A-levels instead. He is taking only 4 subjects this year – maths (two types), physics and economics and next year he will stop the economics and only study maths and physics. This very specialized learning at such an early age would be unthinkable in the US but he is loving it.
The reason he has left home and gone to England is because all the international schools here are changing to study the IB programme instead of A-levels. I personally don’t think that it will make much difference what sort of qualifications a child has to get into university. I believe that all universities will recognise all the main qualifications. (My daughter had no problem being accepted to study in London with her Canadian qualifications.)
It may, however, be harder for someone who hasn’t covered as much material as others to be able to keep up once at university. For example my son, studying GCSE maths (age 16) already knew how to answer my daughter’s boyfriend’s Canadian grade 12 maths (age 18). Just think how much more he will know when he starts university after studying maths for three hours a day for another two years.
It is said that an honours bachelors degree from England is at s at a similar level to a US masters degree. And I have known students from England go straight into a PhD programme in the US with their bachelors degree.
One of the nice things about living in Hong Kong is that you have so much choice open to you and your children. And the children meet people from all over the world. Very quickly they are thinking globally. My younger son is considering doing his tertiary education in Australia.