<P> As with primary schools, students pass from grade to grade regardless of knowledge or academic achievement, the result being that classes often have students of vastly differing abilities learning the same subject material together . In the final year of middle school examination scores become very important for the top students hoping to gain entrance into the top high schools, and for those in the middle hoping to get into an academic rather than a technical or vocational high school . Otherwise, examinations and marks only matter insofar as living up to a self - enforced concept of position in the school ranking system . There are some standardized examinations for certain subjects, and teachers of academic subjects are expected to follow approved textbooks, but generally middle school teachers have more flexibility over curricula and methods than teachers at high school . </P> <P> More than 95% of the middle school students also attend independent owned, after - school tutoring agencies known as hagwon, and many receive extra instruction from private tutors . The core subjects, especially the cumulative subjects of Korean, English and math, receive the most emphasis . Some hagwon specializing in just one subject, and others offer all core subjects, constituting a second round of schooling every day for their pupils . Indeed, some parents place more stress on their children's hagwon studies than their public school studies . Additionally, many students attend academies for things such as martial arts or music . The result of all this is that many middle school students, like their high school counterparts, return from a day of schooling well after sunset . The average South Korean family spends 20% percent of its income on after - hours cram schools, more spending per capita on private tutoring than any other country . </P> <P> High schools in South Korea teach students for three years, from first grade (age 15--17) to third grade (age 17--19), and students commonly graduate at age 18 or 19 . High school students are commonly expected to study increasingly long hours each year moving toward graduation, to become competitive and be able to enter attractive universities, such as SKY (Seoul National, Korea, and Yonsei Universities) or SeoKaPo (Seoul National University, KAIST, POSTECH), which are top universities in Korea that almost all parents and teachers want students to enter . Many high school students wake and leave home in the morning at 5 am . When the school is over at 4 pm, they go to a studying room in the school or to a library to study instead of going home . This is called' Yaja', which literally means' evening self - study' . They don't need to go home to eat dinner since most schools provide paid dinner for students . After finishing yaja (usually ends at 10 pm, but later than 11 pm at some schools), they return home after studying, then return to specialty study schools (which are called Hagwon) often till 2 am, from Monday to Friday . In addition, they often study on weekends . </P> <P> The yaja had not been really' self' study for more than 30 years; all high school students were forced to do it . From 2010s the ministry of education has encouraged high schools to free students of yaja and to allow them do it whenever they want, and many normal public high schools near Seoul are now no longer forcing students do it . But private high schools, special - purpose high schools (such as science high schools, foreign language high schools), or normal schools far from Seoul are still forcing students to do yaja . </P>

When do you start high school in korea