Well... I'm not a religious person. And I don't believe in the supernatural.

I accept the explanation for the existence of life on earth (including human life) that is provided by the theory of evolution.
I don't know why it is you're failing some of your subjects.

But I am personally comfortable in saying that it doesn't have anything to do with the supernatural. Since your mom believes in this stuff, though, if you want to indulge her by praying & wearing what she tells you to wear, I think that's very kind. But, at least from my perspective, it's not going to get you a passing grade on your exams.
It's been many years since I was in school. But I recall one time sitting in a large lecture hall (sweating over my own exam book) while other students were doing the same. When each student had finished her or his exam, s/he was to set the completed exam on a shelf in the back of the auditorium on their way out. Another student, whom I vaguely recognized, walked in late, took someone else's exam from the stack of completed exams, copied it, & put both the pilfered exam, & his own exam, on the pile of completed exams on the shelf. Then he left.
For some people, studying & taking exams comes easily. For others, like me, it was always a chore. I could get good grades if I applied myself. But I really had to work at it. And then... like the guy I mentioned above... some people cheat.

(I also wouldn't be surprised if some students get "a pass" if the professor(s) particularly like them.) I obviously don't know anything about the school you attend. But I feel safe in saying that there's a very down-to-earth reason why you're failing some of your subjects. You just have to figure out what it is. My best wishes to you...