Two of my friends would like to become a Child Psychologist and they are both taking Psychology, Sociology and Health & Social Care.
To get onto a psychology degree, you do not necessary need to take an A level in Psychology, even though it would be useful as you will gain more of an insight in Psychology and you will therefore, have some knowledge on the subject.
Most Psychology degrees ask for Psychology, Biology, Maths, English, History, Economics and similar arts and social science subjects. All of these subjects would be beneficial, but remember to take subjects you know you will enjoy as well!