(whereas you guys get 7 years of high school).
Nope. High school in the US is generally four years.
A levels are the equivalent of SATs. A-levels determine whether we go to university or not.
Yes and no. The SATs are not that important on their own. They are just one part of the college application. For example, my high school GPA really sucked. However, I got into the university that I did because my SAT score was
very high. There are also people I know who had very high GPAs that made up for low SAT scores. Some schools (some of which are considered to be very good) don't even require the SAT exams. In England, the A-levels seem to be one of the primary hurdles to admission at a school, with many schools making an admission offer contingent on the student achieving a certain set of scores.
Also, the SAT is nothing like the A-levels in form and content. The SAT was formerly an IQ test that is now confused as to what it is. The College Board, who administers the exam, says that scores on the exam have a very strong correlation with freshman GPA and that is why they claim that it is useful for admissions committees to look at. The SAT IIs test knowledge in subject areas like the A-levels. However, they are not very rigorous at all. The closest thing that US students take in form and content to the A-levels are the Advanced Placement (AP) exams that many high school students take for early college credit. They cover specific subject areas and are generally considered to be quite rigorous. However, I know of no school who actually requires them for admission, although they can be a major plus for admissions.