For A-levels when you want to teach students at secondary or college; I would take the subject you want to teach and then surround your options; firstly on any other subjects, you may also need to know and then a level similar to the subject. I decided not to carry on into the route of trying to be a teacher in English, but my original choices were English Language, English Literature, History and Photography which all use a similar essay styled type, can all link to each other in a different way and gives me an art alongside three very exam based options. I would then follow with a degree in the field I would want to work in, which from my example would be English.
For primary education, it would probably be better to take a vocational course in childcare or other courses in child development and health and social care. However, if I am right, you will need an NVQ to actually work with younger children. I hope this helps you to some aspect, I did a mass of research into teaching and only really changed my mind when it came to the time to pick our options.