I've found myself in a paradoxical situation. I have failed modules over and over, many modules, some modules more than once. One of the failed modules was introduction to computing. After passing it I felt an urge to write lecture notes because I though that the "official" lecture notes made by two teachers of the computer science department were too shallow and unappealing. I took some time to write it and publish in a free webhosting service.
Now I'm feeling like continuing that type of work, expanding it to more modules, such as physics and calculus. It seems that explaning things with plain english, doing comparisons and following a straight path is kinda easy for me. Although I did fail so many modules so many times.
Is the correlation between learning a subject and having high grades strong?
Conversely, is the correlation between not properly learning a subject and having really bad grades strong?