I used to teach in a cram school in Asia. Traditionally, these were a way for teachers to earn more money. The usual schools had classes all day M, Tu, Th, Fr and half days on Wednesdays and Saturdays. Wednesday and Saturday afternoons were when most students went to lessons at the private cram schools, where they sometimes learned from the same teachers as their regular schools, they were just paying more for it. Some students might have private lessons at the cram schools on other days after school, but those were more expensive.
The reason parents did this was that the exams to get into an academic junior high, high school, or college were very competitive. Everybody knew the rankings of the schools, and your family would not let you attend less than the best school you could get into.
In the old days, exam scores also sorted students into majors. The students with the best scores, got into most highly demanded departments. You might end up in architecture school, for example, because your entrance exam scores were in a certain range, not because you had any aptitude for architecture.
Family expectations do play a big role. In many Asian families, getting good grades and good exam scores are almost the only way to be a good kid. Teenaged girls aren't even given household chores or allowed to get jobs because it would take time away from their studies. Besides, they will learn to do housework the way their mother-in-law wants it done some day.
