@Galich
As for my country,
An international recognition I mentioned (7.5 in IELTS for students majoring in Law, and 6.5 for students majoring in other study programs) is for students who want to go study abroad.
If you apply for Computer Sciences, Mathematics or Physics, IQ tests are usually included in your Mathematics test. However, it depends on private universities themselves.
To graduate high school you have to go through three examinations, first semester's exam, second semester's exam, and national high school's exam. The same 10 subjects for those three exams. Your overall result of high school exams decide whether you can be accepted into Government Universities (in which considered as an honor). Usually, during waiting for results released, students take uni entrance exams provided by many private universities. Taking those uni entrance exams may be just a waste of time and money, but everyone do it anyway.
As for national high school exam, students are separated by zones/provinces. For each zone, there may be thousands of students whose names are sorted (A-Z) are divided into classrooms. and with already assigned seat numbers. You take exams in a completely new environment (i.e. in an unfamiliar school, with strangers both students and inspectors.) Do you guys have this kind of high school exam?