I do psychology (I'm in year 13) and it's a great subject but a lot of work! On edexcel we cover (at AS):
>10 key studies in great depth (aim, procedure, results, conclusion, evaluation) this is detail like exact participant numbers and specific practical details
>About 15 key theories in detail (key terms, key concepts, evaluation and application)
>4 key questions (usually includes application of all relevant theories)
>4 key practicals (aim, procedure, results analysis, conclusion, evaluation)
>A bunch of extra studies in less detail
>Crap ton of research methods and evaluation of all of them
>A bit of maths and stats
So yeah it's quite a lot to memorise and revise but it is really interesting!