I'm in Year 11 currently (only just started on the 28th), and heck yes you can!! If you want to get those grades just put in the effort and trust me it is achievable! Oh and NEVER aim for less than full marks.
But yeah my mini inspirational story is that in Year 9 I was at about a D grade in Science, even with working hard- so in Year 10 I decided to do a heck load more work on it and did everything I needed to do for an A* grade- and I got a lot better surprisingly quickly; began getting As in tests then A*s, and when it came to the end of year actual GCSE Exam for U1, I got an A* in the coursework, full marks in my Chemistry Exam and A*s in Biology and Physics too
I did the same kinda thing in my other subjects and I'm at B+-A* grades in those (we oddly enough only had science exams in year 10 though)
So my point is ANYTHING IS POSSIBLE IF YOU'RE DETERMINED ENOUGH
Good luck