Getting grades like those in your first year 12 mocks isn't unusual, and you've got plenty of time to improve. I would start experimenting with a few different revision techniques now, so that by the time your end of year exams come around, you'll have a strategy that you know is effective for you. Other than that, the best thing you can do is to complete all your homework assignments to the best of your ability and to stick diligently to your deadlines.