Someone will have to explain to me how the US system works

In a nutshell, and based on Michigan's requirements:

The academic year begins in late August and goes through early June. Breaks are frequent, and include Thanksgiving and the day after, two weeks around Christmas and New Year's Day, a week in early spring, and various odd days and half days off. It is rare for the local school system to have two full, uninterrupted weeks at a stretch, because of time given to the teachers for training conferences, parent conferences and such. Through it all, the school must afford 180 days of instruction in the year.

Schooling begins at age five with Kindergarten, a half-day session primarily geared toward teaching the children to follow instructions, take turns and such. There is a limited amount of academic instruction, so that most children know the alphabet, counting up to 20 or so, and can write their own names and a few other words.

Full-time school days start in 1st grade. The public school system offers instruction from grade 1 to grade 12. The exact allocation of grades among school buildings depends upon fluctuations in student population, but generally, elementary school goes to grade 6, junior high (or middle school) encompasses grades 7 and 8, and high school includes grades 9 through 12.

In elementary school, a student is assigned to a particular classroom taught by a single teacher. That class and teacher cover all the different academic disciplines for the entire year -- reading, spelling, penmanship, science, art, arithmetic -- except for subjects like gym or music which require special equipment.

In junior high, the students go from classroom to classroom, according to a class schedule, and they have a different instructor for each subject. A typical junior high schedule might include: English, math, history, science, gym and home ec or shop. There are very few electives available in junior high.

In high school, the schedules become more differentiated, as students pursue courses suitable to their aptitudes and interests. To obtain a high school diploma, a student must satisfactorily complete minimum numbers of courses in English, science, math, history, government, gym, and so on, as designated by the local board of education. Students pursuing college prep tracks will take foreign languages, advanced science and mathematics and such, while students pursuing vocational tracks will take shop, bookkeeping, word processing, and such.

At each grade level, student grading depends largely on the teacher of the pertinent classroom or course. Usually, the grading depends upon both classwork (participation in class, homework, special projects) and examinations (some teachers quiz every week, some give only midterms and finals), but final examinations are usually a significant part of the final grade for a course. A student who cannot obtain a satisfactory grade in a course cannot get credit for it, and if he needs it to advance to the next grade level or to obtain his diploma, he must repeat the course or grade level.

On top of this layer of grading is the recently imposed state testing system, which now tests all students in the state on core subjects (math, science, English) at several points (I think something like: 3rd grade, 7th grade, and 12th grade). The results of the tests affect the funding and autonomy of the schools; schools with poor results are subject to state takeover. And, students who place highly enough receive special state endorsements on their diplomas.

School attendance is mandatory until age 16, which for most students is grade 10 or 11.

After graduation from high school, many students continue to college or a training school. There are hundreds in the US, both public and private, but all require substantial payments of tuition by the students. For a standard academic college bachelor's degree, four years of study is required.

Postgraduate study is required for certain professions. Physicians must attend medical school for four years; lawyers must attend law school for three years.

A list of requirements for a diploma from the local school district, through the adult education program, is here:

Credit Requirements: 2000 Graduation Requirements
English 4 cr.
Math 2 cr.
Science 2 cr.
Social Studies 1 cr. (Economics/Political Science)
U.S. History 1 cr.
Government 1/2 cr.
Electives* 7 1/2 cr.
*Must include 1/2 credit of Word Processing, Introduction to Computers, or an equivalent course. This requirement may be waived for some students. Please see academic advisor for more information.

Each credit represents one academic year of instruction at the high school level, so, one would need four years of English, two years of math, two years of science, one year of social studies, one year of US history, a half-year of government, a half-year of computer use, and 7 years of other. I believe that these requirements vary a bit from the standard requirements; I guess they decided that adults going back to school didn't really need the joy of gym class, stinky lockerrooms and public showers.