Hi

You will be a regular candidate if you join school and start from class 11 after failing in class 12th.

This is because,

Private Candidate are those who give exam but are not enrolled in any school due to some reasons like have failed in 12th and again appearing in the exam to pass.

So, if one fails in class 12th and then again appear for its examination on the basis of his or her previous registration in class 12 without joining any a school then he or she will be a private candidate

but as your going to take admission in school and starts from class11 then you don't need to worry you will be a regular candidate.

In case you are asking about regular and private candidate in regarding with neet then I would like to tell you that even if you pass your class 12th examination as a private candidate , you will be still eligible for Neet 2021 as private candidates are eligible for Neet examination until Supreme Court gives its judgement over the eligibility of private candidate and after that eligibility will depend upon the result of the judgement

Thank you