Because of the importance of the university entrance examination in determining one's career prospects, students are under intense pressure to study long hours. The high school years, especially, are a time when students have little chance to do much except study. The Korean saying "Sleep five hours and fail, sleep four hours and pass" is taken seriously; for three years students typically begin school at 6 a.m. and finish at midnight; some students finish at 10 p.m. and go to hagwons until midnight or 1 a.m. Students can forgo the 10 p.m. to midnight classes and self-study sessions but only with permission from both their parents and their homeroom teacher, and few bother to ask. The schedule lasts seven days a week and is rigorous even during periods of nominal vacation. It is not uncommon during exam periods to see students sleeping during class from exhaustion. Students are encouraged to see themselves as being in fierce competition with their friends and peers.