I think it depend on whether your son is a tough guy ! If the answer is "yes", just let him having a bad feeling and lossing confidence for a short time. Try to explain to him that there are significant differences in the study methods between primary and secondary schools. I would like to remind you that competition still exists and indeed is quite keen in public HKCEE exams. Even you let him studying in a band 2 secondary school and let him have a better feeling now , he may also get into trouble in finding a seat in local Universities in the future. I think the most important point is whether you prefer him to learn from fail or just giving give him an illusion of being a top student in class ! Try to find a tutor to help him, I think after sometime he can get pass or fairly good results in all subjects !
My friend got top grades (no. 1 in 200+ students in decent Primary School,her parents are teachers too) but enter a English Sec School (band 1) and grades plummetted, but the parents failed to support ...... and that was too much for my friend ....
所以中一階段﹐佢感到自信打擊﹐家長的確立﹑肯定﹑支持﹑體諒﹐就是他最大動力 -- 你自己要 let go 對分數的執著﹐你 let go 了﹐孩子看到你在他(眼中)不理想成績﹐你仍然對他接納﹑支持﹑確立﹐這種肯定﹐對一個感到挫折的人﹐不論大人小孩﹐都是勝過催谷的
No need to be such extreme in providing a 99% English environment, I found out that reading both English and Chinese version of the same book does have good effect for both languages.
I recommend the book below and would improve scientific knowledge as well:
George's Secret Key to the Universe
勇闯宇宙首部曲
By Stephen & Lucy Hawking
For Christain families, the Bible should be the prime choice.
I recommend the New International Version Bilingual from The Worldwide Bible Society.
Read the Chinese book or section first, then English one and write a short summary in English as report. The parent must share with the kids, the important part.