The British school system can get confusing. Atleast, I find it to be. Let me try to explain
From the age of 3-11 you attend Primary School. This is just the basic education, obviously compulsory. You sit a SAT exam at the end but it means nothing
From 11-16 is Secondary School. Here you work towards earning your GCSE. It's the minimum education needed to begin working. However if you start working with only GCSEs it's very unlikely you'll ever get a decent job. The average amount of GCSEs something leaves school with is 13. One for every subject, some have doubles such as Science (which can go into triples for the more intelligent kids, I was a double) and English also counts as two.
Next comes the optional education. This is where it gets confusing. From here you can embark on the more traditional and more popular route of A Levels. You can do Vocational courses, Pre-Vocational, Mature Learning Courses, HNCs, BTECs etc etc. A Level is usually the best solution though unless you're aiming for something in particular like Welding or Mechanics
After that comes University. Again, another quagmire. From Degrees, Foundation Degrees, HNDs etc etc. Again, the majority of people do a degree
I doubt that cleared anything up but I hope it helped a little Anyone care to explain the American system to me?