Honestly, I don't know how Chinese, South Korean, Japanese, (etc.) kids do it. They're under such immense pressure to succeed.
A colleague from South Korea explain to me that his daughter, 11yo, back in korea had school from 8:00 until 15:00, then had extra math class from 15:00 until 20:00 -every day- then spend 3 hours on homework. As a west-european, this sounds to me like child abuse, but ok.
It is.
Lack of sleep and leisure time will do more damage in the long run than the short term benefits of 16+ hours of learning a day will ever do good.
Am Hong Kong uni student. I can tell you that the workload in college is significantly lower than in primary or secondary school.
In HK (and I think in China as well), all of your school life leads to 1 important exam, and this exam determines whether you get into uni or not.