The second season of To Aru Kagaku no Railgun (A Certain Scientific Railgun) already confirmed at the Dengeki 20th Anniversary Festival.
The title of the second season is Toaru Kagaku no Railgun S (A Certain Scientific Railgun S).
For the airing date has not been confirmed yet. Though this will be a good news for fans. So please looking forward to watch second season of To Aru Kagaku no Railgun