ACT English: The 6 Grammar Rules That Cover 80% of the Test

Most Students Overthink ACT English — Here's What Actually Matters

Parents, here's a secret that changes how your student should prepare for the ACT English section: out of the dozens of grammar concepts your student has learned since middle school, only six rules account for roughly 80% of the questions on the test.

That's not an exaggeration. We've analyzed thousands of ACT questions across years of official tests, and the pattern is remarkably consistent. The ACT doesn't test obscure grammar trivia. It tests the same foundational rules over and over again — just dressed up in different passages and contexts.

At nGenius Prep, we call these the "Big Six." When students master these rules first, they build a scoring foundation that makes every other English concept easier to learn. Let's break them down.

Understanding the ACT English Section Structure

Before diving into the rules, your student needs to understand what they're walking into. The ACT English section gives students 45 minutes to answer 75 questions across five passages. That's 36 seconds per question — fast, but manageable once you know what you're looking for.

The questions fall into two broad categories:

Usage/Mechanics (~30 Questions)

These are the pure grammar questions. They test punctuation, sentence structure, and grammar rules. This is where the Big Six live, and this is where most students can gain the most points with the least study time.

Rhetorical Skills (~20 Questions)

These questions ask about writing strategy, organization, and style. They're less about "is this grammatically correct?" and more about "is this the best way to say it?" We'll touch on strategies for these too, but the Big Six are your student's first priority.

The Big Six: Grammar Rules That Dominate the ACT

Rule 1: Clauses — Know the Difference Between Independent and Dependent

This is the foundational concept that makes everything else click. An independent clause can stand alone as a sentence — it has a subject and a verb and expresses a complete thought. A dependent clause starts with a subordinating word (because, although, when, since, while) and cannot stand alone.

Why does this matter so much? Because the ACT constantly tests whether students can identify how clauses should be joined. You can't just slap two independent clauses together with a comma (that's a comma splice). You can't put a period after a dependent clause and call it a sentence (that's a fragment).

What the ACT tests:

• •Comma splices (two independent clauses joined by just a comma)
• •Run-on sentences (two independent clauses with no punctuation between them)
• •Sentence fragments (dependent clauses pretending to be sentences)
• •Proper use of semicolons, periods, and conjunctions between clauses

Once your student can quickly identify whether a clause is independent or dependent, they'll see patterns in the answer choices that make the correct answer almost obvious.

Rule 2: Commas — The Six Uses That Actually Matter

Commas are the single most tested punctuation mark on the ACT. Students who guess at comma placement are leaving points on the table. The good news? The ACT only tests six specific comma uses. If your student learns these six uses and applies a simple default rule — when in doubt, leave the comma out — they'll handle comma questions with confidence.

We've written an entire deep dive on ACT comma rules because this topic alone can be worth 5-8 questions on test day. The short version:

1. 1.Separating items in a list
2. 2.Joining two independent clauses with a coordinating conjunction (and, but, or, so)
3. 3.After introductory elements
4. 4.With adverbs and adverbial phrases
5. 5.Isolating non-essential (nonrestrictive) phrases
6. 6.Setting off parenthetical expressions

The critical mindset shift: the default is NO comma. Your student should only place a comma if they can identify which of these six jobs it's doing. If it doesn't fit one of these categories, the comma doesn't belong.

Rule 3: Subject-Verb Agreement

This one sounds simple — and conceptually, it is. The subject and verb in a sentence must agree in number. "The dog runs" (singular). "The dogs run" (plural). Easy, right?

The ACT makes it tricky by putting distracting phrases between the subject and the verb. Consider:

"The collection of rare stamps belonging to my grandfather _____ worth thousands of dollars."

Many students see "stamps" and "grandfather" right next to the blank and choose "are." But the actual subject is "collection" — singular — so the answer is "is."

What to watch for:

• •Long prepositional phrases between subject and verb
• •Sentences where the subject comes after the verb (inverted sentence structure)
• •Compound subjects joined by "or" or "nor" (the verb agrees with the closer subject)
• •Collective nouns (team, group, family) that are typically singular

Pro tip: Have your student mentally cross out everything between the subject and the verb. The agreement becomes obvious once you strip away the distractions.

Rule 4: Verb Tense Consistency

The ACT doesn't expect students to identify the past perfect subjunctive by name. It expects them to notice when a passage that's been written in past tense suddenly and unnecessarily shifts to present tense.

Most verb tense questions on the ACT come down to consistency. If the passage is telling a story in the past tense, the underlined verb should also be past tense unless there's a clear reason for the shift (like stating a general truth or describing something that's still happening).

What to watch for:

• •Unnecessary tense shifts within a paragraph
• •Clue words that signal tense: "yesterday" (past), "currently" (present), "by the time" (past perfect)
• •Past perfect ("had walked") vs. simple past ("walked") — past perfect is for the earlier of two past events

Strategy: Before choosing an answer, read the surrounding sentences. Match the tense to what's around it. If three sentences are in past tense and one answer choice randomly switches to present, that's probably wrong.

Rule 5: Noun-Pronoun Agreement

Pronouns must agree with their antecedents in number and gender. If the noun is singular, the pronoun replacing it must be singular. If the noun is plural, the pronoun must be plural.

The ACT loves to test this with:

• •Ambiguous pronoun reference: "When Sarah told Maria about the award, she was thrilled." Who was thrilled? The ACT will ask your student to clarify.
• •Singular nouns with plural pronouns: "Every student should bring their notebook" — the ACT traditionally treats "every student" as singular, requiring "his or her notebook."
• •Collective nouns: "The team celebrated their victory" vs. "its victory" — context determines which is correct.

What to remember: When your student sees a pronoun underlined, they should immediately look for the noun it's replacing and check if they match in number.

Rule 6: Apostrophes — Possession vs. Contraction vs. Plural

Apostrophe questions are among the easiest points on the ACT — if your student knows the rules. They're also among the most commonly missed because students overthink them.

The three rules:

1. 1.Possession: Add 's for singular nouns ("the student's book"), just an apostrophe after the s for regular plurals ("the students' books")
2. 2.Contractions: It's = it is. They're = they are. Who's = who is. Your student needs to be able to expand the contraction to check if it makes sense.
3. 3.Plurals NEVER get apostrophes: "The dog's are barking" is always wrong. Always.

The it's/its trap: This is the single most tested apostrophe concept on the ACT. "It's" always means "it is" or "it has." "Its" (no apostrophe) is the possessive form. If your student can't expand "it's" to "it is" in the sentence, the answer is "its."

Beyond the Big Six: Strategies That Add Points

The "Shorter Is Usually Better" Principle

Here's a powerful test-taking strategy that applies specifically to the ACT English section: when you're stuck between two grammatically correct answer choices, the shorter one is usually right.

The ACT values conciseness. Wordy, redundant answer choices are almost always wrong. If one answer says "the reason is because of the fact that" and another says "because," the shorter answer wins.

This doesn't mean the shortest answer is always correct — but when your student has eliminated the obviously wrong choices and is deciding between two that both sound fine, going shorter is a reliable tiebreaker.

The "Two Looks" Method

We teach our ACT Blueprint students a method we call "Two Looks":

1. 1.First Look: Read the sentence with the underlined portion and see if anything jumps out as wrong. Check it against the Big Six. If you spot the error, find the answer that fixes it and move on.
2. 2.Second Look: If nothing jumped out, read each answer choice back into the sentence. One will sound clearly better than the others. Trust your ear — but verify with the rules.

This two-pass approach keeps students from spending too long on questions they can answer quickly, while giving a structured fallback for trickier questions.

The Yes/No Question Strategy

Some ACT English questions present a proposed change and ask whether the writer should make it — answer choices start with "Yes, because..." or "No, because..." Here's how to handle them efficiently:

1. 1.First, decide Yes or No. This immediately eliminates two answer choices.
2. 2.Then pick the best reason. Only one of the two remaining choices will give a reason that's actually supported by the passage.

Students who try to evaluate all four answer choices at once waste time and get confused. Decide the direction first, then evaluate the reasoning.

How Rhetorical Skills Questions Work

The remaining ~20 questions on the English section aren't about grammar — they're about effective writing. These test:

• •Transitions: Does the sentence logically connect to what comes before and after?
• •Relevance: Should this sentence be added or deleted? Does it support the paragraph's main idea?
• •Organization: Where should this sentence be placed? What's the most logical paragraph order?
• •Style and tone: Is the word choice consistent with the rest of the passage?

For these questions, context is everything. Your student needs to read the full paragraph, not just the sentence in question. The answer that best serves the passage's purpose and flow is the correct one.

Building a Study Plan Around the Big Six

If your student is starting ACT English prep, here's the order we recommend:

1. 1.Week 1-2: Clauses and comma rules. These two concepts are deeply connected and show up on nearly every test.
2. 2.Week 2-3: Subject-verb agreement and verb tense. These require practice identifying subjects in complex sentences.
3. 3.Week 3-4: Pronoun agreement and apostrophes. These are the quickest wins once the fundamentals are in place.
4. 4.Week 4+: Rhetorical Skills questions and full-section practice tests.

This sequence works because each concept builds on the previous one. You can't master commas without understanding clauses. You can't spot verb errors without finding the subject first.

The Score Impact Is Real

Students who come to us with ACT English scores in the 18-22 range and systematically master the Big Six typically see improvements of 4-6 points on that section alone. That's not because we teach magic tricks — it's because the test is more predictable than students expect, and focused preparation beats random studying every time.

The key word is systematically. Reading a list of grammar rules once isn't enough. Your student needs to practice identifying these patterns in real ACT passages until the recognition becomes automatic.

What to Do Next

If your student is preparing for the ACT and wants structured, expert-guided prep that focuses on what actually matters, explore our ScoreJump program for comprehensive online preparation, or check out our ACT Edge course for self-paced study with real tutor support.

The English section is one of the most improvable sections on the entire ACT. With the right focus on the right rules, your student can see meaningful score gains in just a few weeks.

Ready to get started? Contact us to learn which program is the best fit for your student's goals and timeline.