Can you explain the school system in US to an european that knows nothing about it?
The school system in the United States can be complex, but I'll do my best to explain it in a way that's easy to understand.

The school system in the US usually has three levels: elementary school, middle school (also known as junior high school), and high school.

Elementary school usually begins at age 5 or 6 and lasts 5 or 6 years. Students usually attend classes from Monday to Friday for about 6 hours a day. They study subjects such as English, mathematics, science, social studies, art, music and physical education.

Middle school usually starts at around the age of 11 or 12 and lasts for 2 or 3 years. Students continue to study a range of subjects, but the curriculum becomes more advanced. They also have the opportunity to take part in extra-curricular activities such as sports, music and clubs.

High school usually starts at around the age of 14 or 15 and lasts 4 years. Students are required to take a certain number of courses in core subjects such as English, mathematics, science and social studies, as well as electives in areas such as art, music, foreign languages and vocational training. High schools also offer a wide range of extra-curricular activities such as sports, music, drama, debating and community service.

At the end of high school, students receive a diploma, which is a certificate that they have completed their high school education. They can then choose to go on to college or university, or pursue other options such as vocational training or employment.
Could you provide me with some explanations of terminology. Such as but not limited too, freshman and senior.
Sure, here are some common terms used in the US school system and their meanings:

Terms used to describe in what year a student is in:

1. Freshman: A freshman is a first-year student in high school or college.

2. Sophomore: A sophomore is a second-year student in high school or college.

3. Junior: A junior is a third-year student in high school or college.

4. Senior: A senior is a fourth-year student in high school or college.

Terms used to describe different levels of classes:

1. Elective: An elective is a class that a student chooses to take, rather than one that is required for graduation. Elective classes can vary widely and may include subjects such as art, music, or a foreign language.

2. Core classes: Core classes are classes that are required for graduation, such as English, math, science, and social studies.

3. AP classes: AP stands for Advanced Placement. AP classes are college-level courses offered in high school that can earn students college credit if they pass an exam at the end of the course.

Additional terms used for describing tests and grades:

1. SAT/ACT: The SAT and ACT are standardized tests used by colleges and universities to evaluate a student's performance.

2. GPA: GPA stands for Grade Point Average. It's a numerical representation of a student's academic performance, calculated by averaging all of their grades.

I hope this helps! Let me know if you have any other questions.