Generally if you are a regular school student than you can apply via your school for CBSE BOARD final exam for class 10th or class 12th. But if you have left the school due to either fail in school final exams or were school dropout than you can apply for CBSE OPEN SCHOOL admission form class 10th or class 12th.
All the following categories of students can apply
(A) 9th fail students can take direct admission in class 10th from CBSE OPEN SCHOOL.
(B) 11th fail students can also take direct admission in class 12th from CBSE OPEN SCHOOL in all the streams Arts, Commerce or Science.
(C) 10th passed students with one year gap can also register them self for class 12th admission from CBSE OPEN SCHOOL.