SwiftShort answer
Dropping the lowest quiz raises the quiz average only when the dropped score is below the average. Six quizzes at 88, 92, 76, 90, 84, 95 give 87.5 averaged whole and 89.8 with the 76 dropped — a 2.3-point quiz gain worth 0.35 course points at 15% weight. If every quiz is high, dropping the lowest lowers the average.
Scope and assumptions
Drop rules are set per syllabus and per category; some drop the lowest of a fixed count, others allow a set number of drops across categories. Your syllabus is authoritative. This page is informational and is not an official grade record.
Students treat a drop-lowest rule as a free hall pass. It isn't free, and it isn't always even helpful: dropping a score changes the category average, and that average gets multiplied by its weight. The size of the effect is (new average − old average) × weight — usually small, occasionally decisive.
Pick your situation
- Combining syllabus categories? → Weighted grade guide
- Points earned vs possible? → Grade guide
- What you need on the final? → Final grade guide
What is a drop-lowest rule?
A syllabus clause that removes the lowest score in a category before averaging. It exists to absorb one bad day (a missed bus, a broken laptop) without letting a single quiz decide a letter grade.
How the drop rule enters the formula
Category average (with drop) = (sum of scores − lowest score) ÷ (count − 1) Effect on course grade = (new category average − old category average) × category weight
Worked example: weighted average after dropping a quiz
HIST 150, six quizzes taken, syllabus drops the lowest. Quiz weight: 15%.
| Quiz | Score |
|---|---|
| 1 | 88 |
| 2 | 92 |
| 3 | 76 |
| 4 | 90 |
| 5 | 84 |
| 6 | 95 |
Whole average: (88 + 92 + 76 + 90 + 84 + 95) ÷ 6 = 525 ÷ 6 = 87.5 With the 76 dropped: (525 − 76) ÷ 5 = 449 ÷ 5 = 89.8
Course-grade effect: (89.8 − 87.5) × 0.15 = 2.3 × 0.15 = +0.35 points
Now assemble the full course with the other categories: homework 20% at 91.4, midterm 25% at 82.6, final 40% at 90.25:
| Category | Weight | Average | Contribution |
|---|---|---|---|
| Homework | 20% | 91.4 | 18.28 |
| Quizzes (dropped) | 15% | 89.8 | 13.47 |
| Midterm | 25% | 82.6 | 20.65 |
| Final | 40% | 90.25 | 36.10 |
| Course grade | 100% | 88.50 |
88.50 — a B+ (87–89.9 on the 10-point scale). Without the drop the course grade is 88.15, and the quiz category alone loses 0.35.
Quiz average with one dropped
The mechanics matter more than the example: always drop before averaging, and never average in the discarded score "for reference." A common error is averaging all six quizzes, then subtracting the lowest from the total — which double-counts the drop and understates the average.
Does dropping a score help or hurt?
The average after a drop can only stay flat or rise, because the dropped score is the minimum, and the minimum never sits above the average. Six quizzes at 92, 95, 90, 93, 94, 91:
Whole average: 555 ÷ 6 = 92.5 Dropping the 90: 465 ÷ 5 = 93.0
The gain is real but small, because the 90 sits only 2.5 points below the average. When scores cluster tightly, the drop contributes almost nothing, and a student counting on it to cross a cutoff is counting on nothing.
The genuine harm cases are structural. First, the drop reduces the count: with only three quizzes, dropping one leaves two, and one bad day on a remaining quiz swings the average hard. Second, a drop is only free after the score exists — planning a strategy around a drop you have not earned yet is how students end a term one point short with no rule left to save them.
A drop changes the count, not the weight: use the Exam Weighted Grade Calculator and final exam tool to price the category before and after. The complete guide covers how to calculate a weighted course grade from syllabus percentages.
When does dropping a score hurt?
- Averaging first and adjusting later, which double-counts the drop.
- Assuming the drop always raises the grade; it raises the category average only when the dropped score is below it.
- Planning around a drop before the dropped score actually exists.
FAQ
Q: How does a dropped quiz change your weighted grade? It changes the quiz category average, which is then multiplied by the category weight — a 2.3-point quiz gain at 15% weight moves the course grade 0.35 points.
Q: Does dropping always help? No — it helps only when the dropped score is below your category average. If all scores are high, the gain shrinks toward zero.
Q: What is the drop lowest score grading policy? The syllabus removes the lowest score in a category before averaging; the dropped score never enters the calculation.
Q: Can I choose which quiz to drop? Usually the drop is automatic (the lowest), but some syllabi let students designate one — read the policy.
Q: What if I have a zero? A zero is usually the dropped score — but check whether the zero counts as an attempt or is excluded entirely.
Q: Do dropped quizzes change the category weight? No — the weight stays fixed; only the average that gets weighted changes.
Q: What if two quizzes are tied for lowest? Policy varies; most drop one of the tied scores. Ask the instructor if it matters near a boundary.
Q: How do I check my quiz average with one dropped? Remove the lowest score, sum the rest, divide by the remaining count — then weight it.
Sources: grading and weighting conventions (en.wikipedia.org/wiki/Grading_in_education); weighted arithmetic mean (en.wikipedia.org/wiki/Weighted_arithmetic_mean).
Disclaimer: Drop rules are set per syllabus and per category; some drop the lowest of a fixed count, others allow a set number of drops across categories. Your syllabus is authoritative. This page is informational and is not an official grade record.
Exam Weighted Grade Calculator