I suggest go for a proper degree program not a diploma course. You can pursue bachelors degree in Journalism after your 12th. UTM university offers BA Journalism and Mass Communication course which is pretty good. You can check course details here at: http://www.utm.ac.in/bachelor-of-journalism-and-mass-communication.php Good luck!

Generally 10+2 in any stream is the minimum qualification required for journalism diploma courses. But it may vary depending on the reputation of the institute.