Many years ago I had a student that I did about 4 hours with, who somehow passed Air Law (before I flew with him) but just wouldn't take the Nav exam. I had to almost pay him to buy a watch as he didn't have one and didn't want one. Shortly thereafter he stopped flying and I moved to a club nearer home. About two years later I was at the old club and asked after him. They told me he was very dyslexic and actually could not tell the time, but had been to a very well known ground training / exam "expert" and passed all the exams first time inside a week. I must ask after him again next time I visit my old friends..........