As someone who spent many years in teaching, please let me give you an initial bit of advice: Beware of using abbreviations ;-)
Apart from a few subjects, like 'PE', different schools use different abbreviations for the same subjects. I'm guessing that 'RS' might mean 'Religious Studies', because that's probably the most common meaning given to it. However, in the school where I taught, 'RS' meant 'Remedial Studies'. (Religion was covered in 'RE', meaning Religious Education). The local education authority used 'RS' to mean 'Recreational Sports', meaning things like ice skating!
For some general starting points, relevant to all secondary teaching, see here:
http://www.learndirect-advice.co.uk/helpwithyo urcareer/jobprofiles/profiles/profile1105/
To investigate relevant university courses, use either the 'search' or 'subject search' facility on the UCAS site, to identify possible courses. (If your definition of 'RS' does mean Religious Studies, I suggest trying 'religion' and 'theology' as keywords). Then go to the relevant university website to learn more about the course and the A-level qualifications that are required to get onto the course:
http://www.ucas.ac.uk/search/index07.html
There's more about careers in teaching, here:
http://www.tda.gov.uk/
Chris