Hi,
in the uk we take A levels at the end of our final year at school (at the age of 18). we usually take exams in three or four different subjects, so you would leave school with 3 or 4 A levels as a qualification. as an alternative, there are also AS levels, that are the equivalent of half an A level, so you could have 6 or 7 AS levels instead of a number A levels (ie. 1 A level = 2 AS levels).
these are roughly equivalent to the international baccalaureate system, and they are the last exams you take before you start at university.
hope that makes sense!