10 English Grammar Rules That Trip Up GED® and SAT® Writers

Both the GED® Reasoning Through Language Arts test and the SAT® Reading and Writing section grade you on the same core skill: can you spot and fix a sentence that's broken. You don't need to name the grammar rule out loud. You need to recognize when a sentence is wrong and know how to fix it fast, because both tests are timed and both mix grammar questions in with everything else.

The good news is that most of the points on these questions come from a short list of repeat offenders. Below are the ten errors that show up most often, each with a wrong version and a corrected version so you can see exactly what changes.

1. Subject-verb agreement

The verb has to match its subject in number, even when other words sit between them.

Wrong: The list of expenses are too long.
Correct: The list of expenses is too long.

The subject is "list," not "expenses." Cross out the prepositional phrase ("of expenses") and check what's left.

2. Sentence fragments

A sentence needs a subject and a verb and has to express a complete thought. A fragment is missing one of those pieces, often because it starts with a word like "because," "since," or "although" and never connects to a main clause.

Wrong: Because she studied every night for a month.
Correct: Because she studied every night for a month, she passed on her first attempt.

3. Run-ons and comma splices

A run-on jams two complete sentences together with no punctuation. A comma splice joins them with only a comma, which isn't strong enough on its own.

Wrong: The test was hard I still finished early.
Wrong: The test was hard, I still finished early.
Correct: The test was hard, but I still finished early.
Correct: The test was hard. I still finished early.

Fix these with a period, a semicolon, or a comma plus a coordinating conjunction (and, but, or, so, yet, for, nor).

4. Pronoun agreement

A pronoun has to match its noun in number. "Everyone," "each," "someone," and "a student" are singular, even though they can feel like they mean more than one person.

Wrong: Every student must bring their calculator.
Correct: Every student must bring his or her calculator.
Also correct: Every student must bring a calculator.

Rewriting the sentence to avoid the pronoun entirely is often the cleanest fix on test day.

5. Pronoun case

Use subject pronouns (I, he, she, we, they) when the pronoun is doing the action, and object pronouns (me, him, her, us, them) when it's receiving the action.

Wrong: Me and him went to the testing center.
Correct: He and I went to the testing center.

A quick trick: say the sentence with only one pronoun at a time. "Me went to the testing center" sounds wrong immediately.

6. Misplaced and dangling modifiers

A modifier should sit next to the word it describes. When it doesn't, the sentence ends up describing the wrong thing, sometimes accidentally.

Wrong: Running late for the exam, the calculator was left at home.
Correct: Running late for the exam, she left her calculator at home.

In the wrong version, the calculator is the one running late, which isn't what the writer meant.

7. Parallel structure

Items in a list or comparison should use the same grammatical form.

Wrong: The course covers reading, writing, and how to solve equations.
Correct: The course covers reading, writing, and solving equations.

If one item in the list is a gerund (writing), the rest should be too.

8. Verb tense consistency

Stay in one tense unless the timeline of events genuinely shifts. Switching tenses mid-sentence without a reason is a common error under time pressure.

Wrong: She studies every night and passed the exam.
Correct: She studied every night and passed the exam.

9. Commonly confused words

These don't test grammar rules so much as spelling and word choice, but they show up constantly:

• Their (possession), there (place), they're (they are)
• Your (possession) vs. you're (you are)
• Its (possession) vs. it's (it is)
• Affect (usually a verb, to influence) vs. effect (usually a noun, a result)
• Then (time) vs. than (comparison)

10. Capitalization and apostrophes

Capitalize proper nouns (names, places, specific course titles) and the first word of a sentence, and use apostrophes only for possession or contractions, never for a plain plural.

Wrong: I bought two calculator's for the exam's in October.
Correct: I bought two calculators for the exams in October.

Why this matters on test day

Both tests ask you to identify an error or choose the best revision, which means you're not writing from scratch. You're pattern-matching against a short, predictable list. Once you can name what's wrong in each of the ten examples above without rereading the explanation, you're most of the way to a strong score on the writing questions.

The GED® course's Grammar and Conventions unit works through all of these error types with guided practice, and the SAT® course covers the same territory from the SAT®'s format in Standard English Conventions. If you're starting from the basics, the Grammar Level 1 spine builds the foundation first. Not sure which grammar rules are actually costing you points? Start with a free diagnostic to find out before you spend hours reviewing rules you've already got down.