Considering they’re meant to measure the same thing, the SAT and ACT are surprisingly different tests (and exactly what they’re really measuring is up for debate). Although the results of the two tend to be pretty similar—meaning students who score high on one test will generally score high on the other (making the SAT–ACT score conversion possible)—the actual content and style aren’t so comparable.
But the writing sections of the two are pretty similar. The same concepts are on both tests. You’ll see a lot of grammar, punctuation, and style in the ACT English section, just as you will in the SAT Writing multiple choice sections. And the essays are both in the standard five-paragraph argument style. There are a few key differences, though.
The types of grammar questions
The SAT has three different types of multiple choice grammar questions: two types that give you single, isolated sentences to analyze, and one type that’s based on a full paragraph or two of text. The ACT, on the other hand, only has the latter type. You get a series of nice, long reading passages, easier than what you’d see in the reading comprehension, each with 15 parts of the text marked and 15 questions in the margins that refer to those marked sections.
You’ll have to deal with subject-verb agreement, parallelism, and all kinds of grammar-y whatnot in both tests, so studying that material will help you increase scores on both. But the difference in the structures of the questions makes for some different strategies. “Identifying sentence error” questions on the SAT, for example, should often be read twice. Ideally, you’ll only very rarely read ACT texts twice (usually just for questions that ask about paragraph structure).
In the SAT Writing section, only a few questions are of the “improving paragraphs” sort, and so there aren’t many that deal with the structure of a piece or what extra information should be included. The ACT, meanwhile, has scads of them, since it’s entirely in that longer text format.
Aside from multiple choice questions, there are always the essays to consider. The first notable difference is that you get five more minutes on the ACT. That might not seem like a lot on paper, but 25 minutes and 30 minutes can feel very different when you’re under the gun.
The other differences are a bit subtler. ACT prompts tend to be a bit more “real world” than SAT essay prompts. While the ACT might ask you whether the school district should begin stricter testing schedules, the SAT might ask you whether increased supervision leads to higher productivity. This makes the ACT essay a little bit easier to brainstorm sometimes, but not by much. You still have to draw from your experiences and knowledge outside of what’s given in the prompt, so whether the question is about something abstract or concrete doesn’t change too much. The downside to the ACT is that you might get a question on a specific topic, which looks scary and foreign—the possible repercussions of new law, say—while the SAT, by being so abstract, rarely causes that problem.
The essay is (technically) optional on the ACT, but it’s mandatory on the SAT, so that makes a pretty distinct difference in scoring. Your standard ACT score includes only your performance on the English section (that’s the grammar and writing multiple choice), keeping the essay separate, but if you want to calculate SAT scores, you have to factor the essay score into your overall writing score. So if you’re a master five-paragraph essay writer, capable of spinning golden examples from straw, and sitting on the vocabulary of a spelling bee champion, but you have trouble with some of the grammar tested in the multiple choice questions, you might find your SAT essay score providing a pleasant bump to your writing score. But that won’t help any for your ACT English score—you’ll only see the effect in a separate essay-plus-English score, which doesn’t contribute to your main score.
In the end, though, it’s the scoring that reflects the overall relationship between these two tests. While the setups may be pretty different, the foundations aren’t so much. No matter which test you’re looking at, you need to know grammar rules, good style, and basic essay structure. Those things count more than anything else.