what board you doing english for
my first grade in year 10 for english lit was a 4 and i got a 9 in the real thing, just learn what your exam board wants
for example, my exam board wanted tons of context about Of Mice and Men, so i just spammed 1930's america context in there
for the sciences, just do tons of past papers
biology is just about regurgitating the mark scheme
chemistry, you need to understand a bit of the maths, but again its just about regurgitating the mark scheme for written answers and memorising definitions
physics, just memorise all the equations and you'll do fine, the maths isnt actually hard