See as you have enrolled yourself in 1st PUC then you have registered to the board as a student of 1st PUC. Now as you have been promoted to the next standard then you have no choice but to follow it, if you wish to keep up with this registration. Now if you want to study 1st PUC again (formally) then you have to cancel your registration and have to take readmission in school. Now if you want a 1 year time for self study then you can drop this year by not attending the schools or by filing any formalities as proposed by the school authority. I would recommend you to contact your school authority for the latter case.

To know more about the courses after 10+2 visit the link below:

https://school.careers360.com/articles/courses-after-12th

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