I do bio, psych and sociology and that it was I want to do. wow! I'm in year 13 now and I would definitely recommend doing psychology, obviously. Biology is definitely a plus point as most universities require at least one science (including psychology) but preferably two, the only thing I would say about biology is to prepare yourself for the mark schemes. Sociology is a good choice, particularly given that there is a crime and deviance section also biology and psychology are very content heavy subjects and so having sociology as a subject with less content is very good. However I would say that doing 4 is not the best use of time, I did do 4 at the start of year 12 and dropped the fourth. The only thing I regret is not doing an AS level, lots of universities see maths as an advantage point and so maybe doing core maths, if your sixth form/ college offers it, would be a good idea! Overall all three subjects are very applicable to our chosen field in psychology and there is also a lot of overlap in the three subjects: for example psychology and sociology overlap in terms of research methods.