Probably like 80% of Uni students, they crammed just enough the night before to get through the test (or through the job interview, using the degree they got by cramming the night before its test)....
Having said all of that, I have met some incredibly dumb teachers historically. How they got their jobs was a mystery to me, then and now.
Re the "Teaching the test" complaint I agree with JoeJester. If the test is not faulty it actually tests the abilities, and if the student passes the test it shows that at least on the day of the test they had >x ability which is probably a lot more ability than many *graduating* high school students in our existing system.
If the tests are national standard and properly designed then there should be no problem. If someone complains about "teaching the tests" then what they are really saying is that the tests are faulty, not the system.
As for students of different ability they can be graded and sorted accordingly. The world needs stupid people too, and they may as well know early in life that they are going to have a career in serving fries (and improve their grades or deal with their future early) instead of finding out later. Remember Orwell's "Brave new world"? Sort them out early, and train them appropriately for their future.