fulltimestudent: you are correct of course - one should not generalise too much, however, this is not just a Chinese issue - it is an Asian issue.
One of the major differences is the need for consensus (quite understandable given the history) which leads to conformity of behaviour and thought. Asian students are taught mainly by rote memorisation - for the test....and therefore are often very good at test-taking, if they are a serious student. This learning style doesn't encourage critical thinking though. There is also a passive student/active teacher dynamic that is the crux of the classroom which also (while in some ways positive) encourages 'learning to the test' - and the resulting 'score' is the main focus for most mothers.
I think a mixture of both Western and Asian(?) learning/teaching styles is productive, but quite difficult to implement. Obviously, there are people who operate outside of this stereotype and they are very intelligent people and often leaders in their field. Some take very well to different learning styles - others do not and they are the ones that go home and continue as before.
The sleeping/looking tired isn't always indicative of study - quite the reverse. Many Asian students are not good at time management and are just used to spending lots of 'time' at the desk but the quality of the study is lacking. Long periods of study actually involve lots of social interaction and other stuff maybe slightly (or not at all) connected with study. Confucian thinking definitely focuses on the time spent studying rather than the knowledge - connected to the process of rote memorisation which begins from a very young age, and hence the mother's driving "do it again" mentality.
In my opinion the most unfortunate outcome of this style of teaching/learning is the importance of the 'arrival' not the 'journey' - but I'm not Asian.