First, you need to understand that marks aren’t the only things that count. You need to acquire some knowledge too, that is the purpose of education.
Second, if you really wanna score high marks, remember this, you can’t score high marks if you are studying for the sake of marks.
You have to start to understand your subject and start loving them and never think that they are useless.
I was a topper in my class just because i never tried to by heart things, and i understood all the topics and wrote my exams with confidence. You must trust yourself to do well to actually do well.
One more thing, try teaching your friends/classmates about your subjects, this will help you understand the subject better and help you remember it and also help your friend too. These were my tricks to score high marks.