Hello Ankit ,

I would suggest you to not join NIOS leaving CBSE. There are several factors for this,

• Tough to prepare for the boards , I particularly found this because you had no one to guide me for your board exams academically, Biology and English are not a problem in this front but Physics,Chemistry and Mathematics which is the main JEE subjects, you have to crush yourself to at least score a decent marks in the boards.
• Most universities do not accept NIOS certificate , although NIOS is a recognized board at par with the CBSE. Most uni's do not accept the NIOS certificate, merely because of their perception that the students from NIOS are quite low in subject knowledge.

Hope It Helps

All The Best

This will completely be your wish to either repeat a year in your school or join Nios.

Both has its advantages and disadvantages, though recently NEET and JEE  has started accepting students from NIOS background as well. However, you might face some problems while getting admission to DU or some other colleges. If you have the will, you can study from anywhere. But to suggest, I would say to complete you 12th from your regular board only.

It will completely be your choice, what you would like to do.

Hello,
Don't go for NIOS as they are not any reputed board, some universities doesn't even accept NIOS marksheets, so don't go for NIOS.
Now there are two ways by which you can pass 12th std, one is to go back to your school but if you don't want to get there with your juniors, then there is another way also, you can fill your examination form for next years exam as a private CBSE candidate, you can study at home and can give exams next year but as a private candidate.

For any further query, feel free to ask in the comment section.

Hope this helps, all the best.