What is the difference between a grade B and a grade A essay?

The key to achieving excellent grades in A level is to make your essays as coherent as possible. In each essay you have, you should have a clear line of argument, e.g if you intend to argue to the following: "I affirm that Hector is a tragic hero in the play of The History Boys" You must make sure your argument relates to this throughout. Furthermore, you should aim to use more complex terminology and expand on this to support your initial argument, e.g "the use of the sibilance in "sweet sound" is almost harmonic, evoking emotions of peace and calamity".