The main difference between GCSE and A-level is the structuring of your essays and the sophistication in which you approach your answers. Instead of giving, for example a for and against answer to a yes or no question, the question may require you to answer thematically for instance. However the main difference, especially within your second year is developing synthesis. This requires you to take an overview of the various historical events you have studied and to make links and comparisons with such events across different periods of history, in order to move away from a chronological GCSE-style approach. Analysis is also important here; showing that you understand the significance of the events and how they relate to one another. While it is important to demonstrate in-depth knowledge and revised content, it is perhaps far more important to be able to compare and analyse the events within the bigger picture; honing in on smaller details as you build your argument and to demonstrate to the examiner that you have a well-rounded knowledge of the subject area.