Teachings of suffocated creativity

"I'd rather learn from one bird how to sing than teach ten thousand starts how not to dance."

It happened to me often when I was younger, that I handed in an essay that I felt great about, just to get back a somewhat below average grade a week later. I've always been told that I'm a great writer, but after this happening quite a few times I started to become more hesitant, more restrained in my writing and I felt unable to express my thoughts in the way I considered most suitable because whenever I did, I felt ridiculed by a mediocre grade. By the time I realized what it had come to, I'd lost my passion for writing and when I did have time to be creative, I found myself just sitting there, wondering how to phrase just the simplest thoughts, because I had been entirely stripped of my confidence.
Then, I realized what had led to this.
You see, in an attempt to evaluate all students equally, there has to be some sort of grading scheme. For a student to be given an fair account of how successful he or she has been, the different levels of success need to be carefully defined. Of course, this makes it clear to students which requirements need to be filled and calls for a very fair evaluation, but it also makes it possible for an immensely talented student to perform poorly according to the grade scheme, because though its performance was above all expectations, it did not fill the specific requirements that needed to be filled for the grade to be high. Of course, smart students will realize this and adapt to the scheme, as I did, but it's very restraining and almost painful to limit yourself into fitting into the system.
This pressure that I must put on myself to squeeze into the outline of a perfect student makes me feel like a lesser version of myself.