You have to understand that Japan's schooling structure although similar in some ways is different from ours. Their classes tend to have an average of 40-45 students in a class where in the US it tends to number anywhere from 20-30. Elementary consists of grades 1-6, then there is Junion High School grades 7-9 and finally Senion High School grades 10-12. High School is optional and families have to pay a tuition for it, which is a reason why many start to confuse their High School as College. They are only required to go to school grades 1-9, High School and Junion College/College are optional. Junior High is all about getting high scores to play them in a good High School. High School is mainly about one thing and that is studying and preparing them for their university entrance exams. You have to go to the right university which will lead to a well paid job or employment with a larger Japanese company.
High school is determined by their scores from Junior High. In the US we rely on keeping students near their place of living. But because of this it is not uncommon for a student to spend 2 hours just riding the train or bus and many changes just to get to their school. In some cases it is cheaper for them to stay in the city near the school with a relative or even by themselves so socially they obtain a higher level of freedom and responsibility than the average teenager. Student behavoir is even supposed to be regulated while traveling to and from school, chewing gum, consuming snacks, reading while walking can be prohibited, basically anything that might relfect badly upon the school. Each school has a unique uniform which makes them easy to identify which school they belong too. They even have policies that require them to stand on buses and trains, leaving seats open for other passengers to demonstrate consideration.
In many cases students are already working full time, attending an evening school (cram school) plus High School. Their clases can run as late as 9pm and often makes their days 12+ hours. They have a busy lifestyle if they are working. Since a lot of it is voluntary, commitment is what usually motivates most students. In the US we rely on parental pressure for our children to have to go to school, where the students in Japan make a lot of their own choice. This usually is why Japanese although the same age as US counterparts are considered more socially mature and attentive.
Mainly for these reasons is why people will confuse College for High School and vice versa. It will also be why there is someone who is 16 living in the city by themselves or a dorm like area, because of the High School they were placed in. We in the US tend to think if they are living on their own, paying a tuition, that they are in College but in reality is just High School.
