Detailed Instructions: In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.
Problem:Article: As a student, you must be excited to know something about American school students. In fact, just like in China, in the United States, high school is usually divided into two periods, the first two or three years are called "junior high school" and the other is "senior high school". In China, children enjoy free education of nine years, but in the United States, the students enjoy free education(which will be started when they are about 6 years old) until they are 18 years old. As a result of the free education system, American children have little difficulty in going to senior high school. American high school students can take part in a lot of activities outside of the classroom. The activities are organized by the school, such as joining a music group or a sports team. Certainly, just like us students in China, American students have to work hard in order to get good marks if they want to go to a good university. They take classes in all kinds of subjects all through the high school period. And students with low marks at the end of a school year are still allowed to go on to the next grade. In American high schools, there is fighting or hurting or other kinds of bad behaviors. So children who want to go to university are often sent to suburban high schools, where most students want to go to university and the atmosphere is quite different.
Answer: education of American high school
Solution:
This passage mainly tells us about _ .