The ACT Writing Test is optional, costs an extra $25, and doesn’t touch the composite score. Most colleges dropped the requirement after the SAT eliminated its own essay in 2021; schools like MIT, UNC-Chapel Hill, UVA, and Michigan no longer ask for it. That has cut the number of students who sit for it, but it hasn’t cut the amount of time some test-prep programs spend drilling grammar rules to prepare for it. The mismatch matters, because the data on what actually raises an essay score points somewhere else entirely.

Most ACT writing prep treats the remaining exam as a grammar test. It isn’t. ACT scores the Writing Test on four domains—Ideas and Analysis, Development and Support, Organization, and Language Use and Conventions—and Language Use and Conventions is only one of the four. Grammar instruction does not move that score. Argument construction does.

ACT’s own rubric makes the weighting explicit. Three of the four domains reward reasoning: generating a position, supporting it with developed examples, and organizing the argument so the relationship between claims stays visible to a reader who disagrees. Only the fourth domain touches sentence-level mechanics, and even there the rubric asks whether errors interfere with meaning, not whether a student can identify a dangling modifier. A perfectly punctuated essay that restates the prompt without taking a position still scores low across the other three domains.

This isn’t a new argument. George Hillocks reviewed more than 500 studies of composition instruction for his 1986 synthesis, Research on Written Composition, and found that teaching grammar in isolation does not raise the quality of student writing. In several of the studies he reviewed, it lowered quality, because time spent diagramming sentences is time not spent practicing the skill the test actually measures: building and defending a claim. Hillocks was blunt about the cost, writing that schools imposing systematic grammar study on students in the name of teaching writing did them “a gross disservice that should not be tolerated.”

Steve Graham and Dolores Perin reached a similar conclusion from a different angle. Their 2007 meta-analysis of 142 studies, Writing Next, ranked instructional strategies by effect size. Explicit strategy instruction, summarization, and sentence combining produced strong, measurable gains in writing quality, with sentence combining showing one of the largest effects in the report. Isolated grammar instruction was one of the few strategies with a negative effect size, meaning the average study measured students getting worse, not better.

Yet classroom time often skews the other way. Arthur Applebee and Judith Langer’s 2011 survey of writing instruction in U.S. middle and high schools, published in English Journal, found that a large share of classroom writing consists of short, mechanical tasks rather than extended argument. The mismatch surfaces on test day. Students drilled on comma rules face a prompt that asks them to take a position, weigh it against a competing perspective, and defend it with developed reasoning, a skill many were never given enough time to practice.

For the students who still need the score, and for the shrinking list of colleges that still request it, prep time is the variable that matters most. Spend it building a position, qualifying it against an opposing view, and supporting it with specific, developed reasoning. Save the comma drills for the in-class essay, where conventions actually factor into a grade. On the ACT Writing Test, grammar is the smallest piece of the rubric. Argument is three-quarters of it.

Further Reading