Hey!

It is mentioned on the official website of CBSE that concept of pre-board exams does not come under the purview of CBSE. It is a school's own prerogative.
Schools conducts the pre board/pre-pre board exams. These exams are onlyy conducted to help students understand the pattern of actual board exams and make them ready about it. If you are not able to write these exams, then you must notify the school authorities.

Thankyou