The CBSE Best of Five rule allows Class 10 students who studied six main subjects to drop their lowest-scoring subject from their aggregate percentage calculation. The aggregate is then computed from only the five best subjects — typically the four scholastic subjects plus the highest-scoring elective.
This benefits students whose performance in one subject (often a language or an optional like Computer Applications) was dramatically weaker than their other subjects. Without Best of Five, a single bad paper in a sixth subject could drag the overall percentage by 3-5 percentage points.
Formula:
Aggregate (%) = (Sum of marks in 5 best subjects ÷ 500) × 100
The five subjects must include the four scholastic subjects (Maths, Science, Social Science, two languages — typically English and Hindi). The "Best of Five" almost always means replacing the second language or the additional elective with whichever is highest.
CBSE's official position is that the universities and colleges decide whether to use Best of Five for their cutoff — CBSE itself reports both the 5-subject and 6-subject aggregate on the marksheet. Delhi University, for example, has historically used Best of Four (4 scholastic only) for arts streams.
The rule does NOT apply to Class 12 — that's an aggregate of all four scholastic subjects plus one elective, with no "best of" smoothing.