Hello,

No, if you fail in class 12th science stream you only have to repeat one year . According to CBSE , if someone fails in class year they have to repeat only class 12th. You can also give compartment exam if you failed in one subject to clear that subject.

You can also give 12th exam from NIOS to complete your HSC Education.

You can click at this link to read more about CBSE Exams - https://school.careers360.com/exams/cbse-class-12th

You can click at this link to know more about NIOS - https://school.careers360.com/exams/nios-class-12

Hope this was helpful.