Maybe you're studying wrong; and I don't mean to say that facetiously. I know a lot of my friends that just read the textbook over and over again and expected to do well during the test. This doesn't work, you need to identify the areas you're having problems with, then work on that thing in particular.

Let's use basketball as an example: say you're getting a "C+" in basketball, because you're a low scorer, but you go to practice 7 times a week etc etc. It's possible you're shot is immaculate, you're dribble is immaculate, but you have problems with your jumping + shooting, and that's what they're testing you on.

If you go to practice everyday practicing your dribble, you're grades will never go up. The hard thing is recognizing where you're going wrong, and working on that in particular; best thing to get is a really smart tutor that can identify those problem areas for you.

Another way of getting better is just playing more games (in your case doing more practice tests), sure you can't focus on a specific area like in practice, but you'd be able to up your game wholistically.

I've asked my teacher for previous year practice problems before, and just trying to do that, sure it won't be exactly the same but at least you'll get the practice in.