The majority of people entering journalism are graduates, so taking a relevant university course might help (but it's still not essential).
Information on careers in print journalism is here:
http://www.learndirect-advice.co.uk/helpwithyo urcareer/jobprofiles/profiles/profile124/
For broadcast journalism, see here:
http://www.learndirect-advice.co.uk/helpwithyo urcareer/jobprofiles/profiles/profile1351/
When seeking employment, qualifications can, of course, be useful but experience often counts for far more. I started writing sports reports (initially unpaid but later for modest fees), for my local newspaper, when I was 14. Later, when I went into teaching, I taught a 15-year-old lad who had regular columns in two computer magazines. (He was earning a good deal of money from writing them).
I currently work mainly as a freelance journalist. Although I've now got some formal qualifications (gained through evening classes), journalism is still a career where it's your ability to do the job which counts well ahead of any 'bits of paper'. I'm definitely NOT trying to put you off seeking formal qualifications but I AM trying to persuade you to start writing (and submitting your work for possible publication) NOW!
Give it a go. It can be fun. If you don't enjoy it, you're probably looking at the wrong career anyway :-)
Chris