About the high schools, it is strict, yes. You have to rank high in the NMET (there is no official "pass line"; which college you can choose depends on your national rank).
It is very stressing place, especially in the senior year. From my experience, you have to get up at 5:30, memorizing knowledge points (in China they only want you to know, not to understand), eating breakfast, listening to the teacher explaining yesterday's exams, eating lunch, performing an exam, eating dinner, listening to the teacher explaining various problems, memorizing knowledge points again, and go to bed around 22:00. Rinse and repeat. You study 6 days a week and the free day is usually filled up with homeworks. You also have about 3 monthes of holidays (mid-Jan to late-Feb, early-Jul to Sep 1) but they are usually filled up with homeworks as well.