Yes you can repeat 12th in the same school and it's a very good thing that youre thinking about giving the exam again and you'll get good marks this time

Hello

Of course, you can repeat 12 as a regular candidates or as private candidates. It should be completed your decision. Even you can choose different boards and also different stream.

This time during preparation be focused and devoted towards your study. You just have to find scoring areas and practice enough to gain confidence. After that you should take next step for working on weak parts. In this way follow one step at at a time.

May you succeed.