3 Rarely Tested SAT and ACT Grammar Rules (You Still Should Know)

Bonus Material: Rarely Tested ACT/SAT Grammar Rules Worksheet with FREE Practice Questions

We discuss the 13 major grammar rules you need to know for the ACT/SAT in our Complete Guide to ACT and SAT Grammar Rules.

3 of those 13 rules appear relatively infrequently on both tests. 

But this doesn’t mean you should overlook them!

In fact, your proficiency in these 3 rules can be vital for squeezing in those extra points on Test Day. This can be particularly vital for high-scoring students.

What’s more, the concepts we discuss in this post are essential for writing style in general. 

This can be essential for crafting a stellar SAT or ACT essay or even college application essay.

Before reading this post, get a head start on practicing these rules by downloading our free rarely tested grammar rules worksheet, which includes practice questions and more. Grab this below.

Here’s what we discuss in this post:

  1. 3 Rarely Tested Grammar Rules on the ACT/SAT
  2. 3 Guided Examples
  3. Bonus: PrepMaven’s Rarely Tested ACT/SAT Grammar Rules Worksheet

3 Rarely Tested Grammar Rules on the ACT/SAT

The following 3 SAT and ACT grammar rules cover the following:

  • Modifiers
  • Idioms
  • Parallelism

Rule #1: Modifiers must be placed correctly.

A “modifier” refers to a word or group of words that provide more information about a certain subject. In most Modifier questions on the SAT or ACT, a modifier is a descriptive phrase that provides additional details about a subject, often appearing at the start of a sentence.

Here are some examples of modifying phrases that might offer further details about a specific subject:

walking down the street

bespectacled and grimacing

associated with ancient tradition

In general, modifiers and modifying phrases must be right next to whatever it is they are modifying! Take a look at these sample sentences that use the modifying phrases above:

Walking down the street, my friend and I took in the gorgeous sunset.

Bespectacled and grimacing, the professor made his way to the lectern.

Associated with ancient tradition, the practice of ancestral worship appears in many cultures.

In all of these examples, the modifying phrases are placed directly next to the subject they are modifying. Misplaced modifiers are called “dangling modifiers,” and these incorrectly modify a subject. Here are the same examples written with dangling modifiers:

My friend and I took in the gorgeous sunset, walking down the street. 

The professor made his way to the lectern, bespectacled and grimacing.

The practice of ancestral worship appears in many cultures, associated with ancient tradition.

Technically, due to the misplacement of modifiers, these sentences declare that it is the sunset that is “walking down the street,” the lectern that is “bespectacled and grimacing,” and the cultures that are “associated with ancient tradition.” In reality, the friends are walking down the street, the professor is bespectacled and grimacing, and the practice of ancestral worship is associated with ancient tradition.

Modifiers appear every so often on ACT English and SAT Writing & Language, and generally with higher frequency on the ACT. How can you tell that you’re dealing with a Modifiers question on either test?

Look at those answer choices and pay attention to what’s changing between them. If you see that word order (syntax) changes, this is a good sign that you’ve got a Modifiers question on your hand. You’ll see this in action in the Guided Examples section of this post.

Rule #2: Utilize the appropriate idiom, when applicable.

An “idiom” is a fixed component of a language. Idioms are often hard to translate into other languages, like the English phrase it’s raining cats and dogs. It can be equally difficult to learn an idiom in another language–most language learners must simply memorize these turns of phrase.

Idioms do appear on ACT English and SAT Writing & Language, but in very specific ways. Yes, these questions are often easier for native English speakers, but that doesn’t mean they aren’t fair game for all test-takers, regardless of English proficiency.

That’s because Idiom questions on the ACT and SAT generally have to do with the following:

  • prepositional phrases
  • homonyms

Prepositions help show relationships between places, things, people, ideas, time, and more. Here’s a list of the most commonly used prepositions in the English language.

on at with of before
without in to at by
into toward behind against for
as from about around after

Small, functional words, prepositions are easy to overlook. However, many prepositions are idiomatic, especially when associated with certain adjectives and verbs. Take a look at these phrases, for example, that must be connected with one specific preposition.

  • accustomed to
  • protest against
  • associated with
  • curious about
  • necessary for
  • at last
  • in general
  • as a means of
  • by all means
  • from time to time

These are all fixed idiomatic phrases. We wouldn’t say, for example, “associated on” or “curious into.” Much like subject-verb agreement, our ears can often tell when an idiomatic phrase is incorrect, but it’s also vital to ensure your familiarity with some of these commonly tested idioms as they can be easy to breeze by!

The SAT and ACT are also interested in your capacity to distinguish between certain homonyms, words that sound the same but have key differences in meaning.

Here are some very common homonyms that have appeared on official SAT and ACT practice tests:

  • affect vs. effect
  • than vs. then
  • fair vs. fare
  • whose vs. who’s
  • its vs. it’s
  • their / there / they’re
  • your vs. you’re

Make sure you know the difference between these homonyms and, more importantly, that you can apply your knowledge of these differences in context!

How can you tell that you’re dealing with an Idioms question on ACT English or SAT Writing & Language?

Once again, scan your answer choices and identify the differences between these choices. You might notice that 2 answers, for example, reference “than,” while the other 2 reference “then,” or that each answer includes a different preposition. These are all great indicators of an Idioms question.

Rule #3: Apply parallel structure for comparisons or items in a list.

Parallelism isn’t just a concept that appears in math. It also concerns grammatical structure, especially with respect to comparisons or lists. Basically, parallelism in the world of English grammar involves making sure everything matches!

To apply parallel structure, ensure that items in a comparison or list are in the same form, category, and/or number. A list includes three or more words or phrases separated by commas. A comparison involves 2 words or phrases and may include the word “than.”

In this next example, the verbs in the list all have the same form (-ing):

Desmond spends his days at the library photocopying, transcribing, and cataloguing articles.

Here, the nouns in the list are all singular, reflecting parallelism in number:

Someday I hope to invest in a car, a retirement account, and a rental property.

Yes, it would be technically grammatically incorrect to list out a mixture of singular and plural nouns (i.e., Someday I hope to invest in a car, several homes, a retirement account, and three rental properties).

Lastly, in this next comparison, notice how the sentence compares nouns that adhere to the same “category:” i.e., the “car enthusiasts of this show” and “those” of “past events.” This is parallel structure, too, as it’s technically grammatically incorrect to compare things that are not in the same category (i.e., comparing a “person” and a “car” or a “pen” with a “book”).

The car enthusiasts at this road show, however, seemed far less interested than those of past events.

How do you know if you have a Parallelism question on your hands on the ACT or SAT? Be on the lookout for the word “than” in the sentence’s context, as this indicates a comparison. If you see a list, scan the answer choices and identify what is changing, as lists can be fair game for comma rule application or parallelism.

Ready to apply these grammar rules in practice? Download our free worksheet for these rarely tested concepts now.


3 Guided Examples: Rarely Tested SAT and ACT Grammar Rules

The key to mastering these grammar rules on the SAT/ACT truly lies in seeing how they are tested, which can feel unfamiliar to students. That’s what can make the ACT and SAT challenging in general–these exams test familiar concepts in unfamiliar ways!

We’ll walk through 3 guided examples that test these 3 grammar rules now, each taken from an officially released SAT or ACT practice test.

Guided Example #1: Modifiers

This Modifiers question comes from SAT Official Practice Test #1.

Modifiers Questions on the SAT and ACT

We can tell that this is a Modifiers question because each answer choice presents a different word order for the same ideas expressed in this sentence. Answer B, for example, begins with “colleagues,” while answer D begins with “I.”

The first thing we’ll want to do here is read for context. What is this sentence trying to say? When we read carefully for context, we see that the first part of this sentence is an incomplete idea: having become frustrated trying to solve difficult problems. This is a descriptive clause designed to modify the subject who is “frustrated.”

Remember the golden rule of modifiers: modifiers and modifying phrases must be right next to whatever it is they are modifying. The subject that comes immediately after this descriptive clause must be the subject who is “frustrated.”

Does it make sense for “ideas” to be frustrated? Not really. We can eliminate C. The same goes for the answer choices that reference “colleagues,” as it’s clear that the narrator (“I”) is the one who is frustrated. We can eliminate A and B and select D.

Here’s how the new sentence would read with correct modifier placement:

Having become frustrated trying to solve difficult problems, I missed having colleagues nearby to consult. 

Guided Example #2: Idioms

This Idioms question comes from SAT Official Practice Test #1.

Idioms Questions on the SAT

How do we know that this is an Idioms question? For one thing, the answer choices contain three prepositions (as, like, for) and one verb infinitive (to be).

Reading for context, we also see that this question concerns the verb “serves” and the preposition that fits with it idiomatically. Many students will be familiar with the phrase serves as. Given that the sentence describes the functions and characteristics of Greek yogurt, it makes sense for us to choose answer B here.

This is how the corrected sentence would read:

Nutritionists consider Greek yogurt to be a healthy food: it is an excellent source of calcium and protein, serves as a digestive aid, and contains few calories…

If this question stumped you, try plugging in the other answer choices. Notice how “serves like a digestive aid,” “serves to be a digestive aid,” and “serves for a digestive aid” all sound a little off, indicating incorrect idiomatic expression.

Guided Example #3: Parallelism

This Parallelism question comes from ACT Official Practice Test #3.

Parallelism Questions on the ACT and SAT 

It might be tough to identify this question as a Parallelism question at first glance. However, the key lies in the answer choices themselves. Notice how each answer choice generally expresses the same idea but includes different pronouns (she, her, one), syntax, and length.

Context shows us a list describing what the narrators love about this individual: “her loyal companions,” “her bravado.” What’s the golden rule of Parallelism? Items in a comparison or list must be in the same form, category, and/or number.

We need to choose the answer choice that includes the same possessive pronoun (“her”), for one thing. This only eliminates answer J, which doesn’t include “her.” However, notice how H is the most concise expression of the idea here: her freedom to do what she wanted. There’s no need for the extra words expressed in answers F and G.

Here’s how the new sentence would read:

We loved her loyal companions, her bravado, and her freedom to do what she wanted.

Download Our Rarely Tested Grammar Rules Worksheet

Just because these questions appear relatively infrequently does not mean that you should overlook them in your test prep!

We encourage students to hone their skills in modifiers, idioms, and parallelism by working through the additional practice questions and guided examples in our free 3 Rarely Tested SAT and ACT Grammar Rules worksheet.

With this worksheet, you’ll get: 

  • A recap of the three rules we discussed in this post
  • Guided examples of questions from official practice tests
  • Practice questions with detailed answers/explanations 


Kate_Princeton Tutoring_AuthorBio Kate M.

Kate is a graduate of Princeton University (B.A. in English Literature and Interdisciplinary Humanities) and Boston University (M.F.A in Creative Writing). Over the last decade, Kate has successfully mentored hundreds of students in all aspects of the college admissions process, including the SAT, ACT, and college application essay.