Year 12 predicted grades

I'm going into year 12 on Friday, how do I get all A*s predicted? I'm taking bio, chem, physics, and maths. My GCSE grades for each subject: Bio: 8, Chem: 8, Maths: 8, Physics: 8. I've heard that some sixth forms predict grades based off GCSEs which I think is absolute ********. I've been working so hard during the summer I've finished some modules and done practice questions for all of my A levels. Surely if I get 100% in every sixth form assessment I do then they CANNOT predict me less than A* right? Like is it even possible to be predicted 4 A*s? Or am I doomed because of my GCSEs?

You won't get predictions now just target grades. We give predictions towards the end of Year 12 and 'working at' grades before that.

So how would I get all A* s predicted grades at the end of Year 12??