Grammar Rules You Must Know for SAT Writing

Grammar Rules You Must Know for SAT Writing

Since 2024, the SAT has been a digital adaptive test that you'll complete in about 2 hours and 14 minutes. The test is scored on a scale of 400–1600 and consists of two main sections: Reading and Writing, and Math. For all Math questions, you'll have access to Desmos, a powerful graphing calculator that can help you work through complex problems more efficiently.

SAT Writing can feel overwhelming because there seem to be endless grammar rules. But in reality, the test focuses on a specific set of rules that show up over and over. If you master these 12 rules, you'll catch the majority of errors. Let's walk through each one with examples so you know exactly what to look for.

Subject-Verb Agreement

The subject and verb must agree in number. This sounds obvious, but the SAT hides the subject with prepositional phrases. "The group of students are going to the store." Wait—is it "group" or "students"? The subject is "group" (singular), so it should be "is going," not "are going."

Trick: Cross out the prepositional phrase (of students) and the agreement becomes obvious. "The group is going." That's your clue that "is" is correct.

Pronoun Agreement

A pronoun must agree with its antecedent in number and gender. "If a student forgets their textbook, they should ask the teacher for a copy." The antecedent is "student" (singular), so "they" seems wrong—but modern grammar allows singular "they." However, older rules would require "he or she." The SAT tests this constantly.

Watch for vague pronouns too. "The school board decided to close the library because it was too expensive." What's "it"? The library or the decision? If the sentence is unclear, it's wrong.

Verb Tense Consistency

Within a sentence, verb tenses should be consistent unless there's a reason for them to change. "She walked to the store and buys milk." That's wrong—it should be "walked and bought" (past) or "walks and buys" (present). The SAT will give you sentences that jump between tenses to test whether you're paying attention.

Exception: If the sentence describes something that was true at different times, tense shifts are okay. "By the time she arrived, I had already left." Past perfect (had left) makes sense because it was earlier than the simple past (arrived).

Comma Splices and Run-On Sentences

You can't join two independent clauses with a comma alone. "The test was hard, many students failed." That's a comma splice. Fix it by: (1) adding a conjunction: "The test was hard, and many students failed." (2) using a semicolon: "The test was hard; many students failed." (3) making it two sentences. (4) making one clause dependent: "Because the test was hard, many students failed."

Sentence Fragments

A sentence needs a subject and a verb. "Running toward the goal." That's a fragment—who's running? "She was running toward the goal." That's complete. The SAT often tests fragments disguised in longer passages.

Parallel Structure

When you list items or ideas, they should be in the same grammatical form. "She likes running, swimming, and to hike." That's not parallel. It should be "running, swimming, and hiking" (all gerunds) or "to run, to swim, and to hike" (all infinitives). The SAT loves this rule.

Parallel structure also applies to comparisons: "She is taller than him" not "She is taller than he is" (though that's technically correct, the SAT wants parallel structure). And comparisons must be clear: "She likes carrots more than salad" vs. "She likes carrots more than he does."

Modifier Placement

A modifier should be placed next to what it modifies. "Walking through the park, a dog jumped on me." Who was walking—the dog or me? It's ambiguous, so it's wrong. It should be "While I was walking through the park, a dog jumped on me." or "A dog jumped on me as I walked through the park."

Who vs. Whom (and Relative Pronouns)

Who is subjective (the subject of a clause); whom is objective (the object of a verb or preposition). "The teacher, who helped me yesterday, is absent today." (who is the subject of helped) vs. "The teacher whom I asked yesterday is absent." (whom is the object of asked). If you're unsure, try replacing with he (who) or him (whom). "He helped me" = who. "I asked him" = whom.

The SAT also tests relative pronouns: "The book which I read" is technically correct (though "that" is more modern). The key is using the right one for the context.

Apostrophes for Possession and Contractions

Use an apostrophe for possession: "the student's book" (one student), "the students' books" (multiple students). Don't use apostrophes for pronouns: "its" not "it's," "hers" not "her's," "yours" not "your's."

Contractions need apostrophes: "can't," "don't," "it's" (it is). The SAT tests whether you confuse "its" (possessive) with "it's" (it is). Tip: if you can replace it with "it is" in the sentence, use "it's." Otherwise, use "its."

Dangling Modifiers

Similar to misplaced modifiers but more subtle. "Having finished my homework, Netflix was calling my name." The modifier "having finished my homework" doesn't attach to a subject—who finished homework? It should be "Having finished my homework, I felt Netflix calling my name." The subject right after the modifier must be the one doing the action.

Article Usage (A vs. An)

Use "a" before consonant sounds: "a book," "a yellow apple." Use "an" before vowel sounds: "an apple," "an hour" (h is silent, so it sounds like a vowel). The SAT occasionally tests this, especially with words where the sound differs from the spelling.

Commonly Confused Words

The SAT tests homonyms and near-homophones: "their" (possessive), "there" (location), "they're" (they are); "to" (preposition/infinitive), "too" (also), "two" (number); "its" vs. "it's"; "your" vs. "you're"; "whose" vs. "who's." These are drilled constantly, so make sure you know the difference.

Wordiness and Redundancy

The SAT prefers concise writing. "In this day and age, due to the fact that technology is advancing at a rapid pace, we must consider the future possibilities that lie ahead." That's bloated. Better: "Because technology is advancing rapidly, we must consider the future." Shorter, clearer, better.

The SAT will give you five versions of a sentence, and one will be cleaner and more direct. Trust the shorter answer unless it loses meaning.

How to Study These Rules

Don't memorize these in isolation. Work through real SAT practice questions and notice which rules appear. When you miss a question, identify which rule was tested. Over time, you'll develop a sense for what sounds right and wrong. Keep a list of rules that trip you up personally and review it weekly.

Grammar rules aren't arbitrary—they exist to make writing clear and professional. Once you see the logic behind them, they're much easier to remember and apply.

Ready to put these strategies to work? SimpUTech's AI Study Coach gives you personalized SAT practice that adapts to your weaknesses and tracks your progress. Start your free 3-day trial at simputech.com.