Why Punctuation Matters on the SAT
Punctuation questions make up roughly 15-20% of the Reading & Grammar section. The SAT tests a small, predictable set of rules. Master these and you'll pick up easy points every test.
The 4 Punctuation Rules the SAT Tests
1. Commas with Independent Clauses
Two independent clauses need a comma + coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so).
Correct: She studied hard**,** and she aced the test. Wrong: She studied hard**,** she aced the test. ← comma splice
A comma alone CANNOT join two independent clauses.This is the #1 tested punctuation rule You need a comma + conjunction, a semicolon, or a period.
2. Semicolons
A semicolon joins two independent clauses without a conjunction:
Correct: She studied hard**;** she aced the test.
The clauses on both sides of a semicolon must be able to stand alone as complete sentences.
Quick Test: Cover one side of the semicolon.
Is it a complete sentence? Do the same for the other side.
Both complete? → Semicolon is correct.
3. Colons
A colon comes after an independent clause and introduces:
- A list
- An explanation
- An elaboration
| Correct | Why |
|---|---|
| She had one goal**:** ace the SAT. | Independent clause before colon |
| She needed three things**:** focus, practice, and sleep. | Introduces a list |
Wrong: She needed**:** focus, practice, and sleep. ← "She needed" is not a complete sentence.
4. Apostrophes
The SAT tests two uses:
Possessives:
- Singular: the student**'s** score
- Plural: the students**'** scores
- Irregular plural: the children**'s** books
Contractions vs. Possessives:
| Word | Meaning | Example |
|---|---|---|
| it's | it is / it has | It's a hard test. |
| its | belonging to it | The test lost its appeal. |
| they're | they are | They're studying. |
| their | belonging to them | Their scores improved. |
| there | a place | Put it there. |
Decision Flow
graph TD
A[Two clauses?] -->|Yes| B{Are both independent?}
B -->|Yes| C{Is there a conjunction?}
C -->|Yes - FANBOYS| D[Use comma + conjunction]
C -->|No| E[Use semicolon or period]
B -->|No - one is dependent| F[Use comma if dependent clause comes first]
A -->|No - introducing a list/explanation| G{Is there an independent clause before?}
G -->|Yes| H[Use colon]
G -->|No| I[No punctuation needed]
Common Mistakes
- Comma splice — Using a comma to join two independent clauses without a conjunction
- Semicolon before a dependent clause — "Although she studied**;** she failed" is wrong because "Although she studied" is not independent
- Colon after an incomplete sentence — The clause before a colon must stand alone
- it's vs. its confusion — If you can replace it with "it is," use it's. Otherwise, use its.
SAT Strategy
On the SAT, when you see a punctuation question, first identify whether each clause is independent or dependent. This single step eliminates 2-3 wrong answers immediately.
The "Period Test": Replace the punctuation with a period. If both sides work as complete sentences, a semicolon or comma + FANBOYS is correct. If they don't, you need different punctuation.