As per most of the boards, if you want to give the 12th board then you have to register yourself under the board from 11th and on passing 11th you can only opt for the 12th examination. So if you want to do in correspondence you have to do it for both 11th and 12th or if you want to do in regular mode then go for it from the starting.

I hope this answer helps. All the very best for your future endeavors!