Essential Steps to Improve High School Writing

Grammar mistakes are often what teachers notice first, even when the underlying ideas in an essay are strong. A handful of specific, common errors account for most of the marks students lose at the sentence level.

The encouraging part is that grammar improvement doesn't require memorizing an entire rulebook. A small number of recurring error types account for the vast majority of marks lost, which means targeted practice on just those patterns delivers most of the available improvement.

Step 1: Learn to Spot Run-On Sentences and Comma Splices

A comma splice happens when two genuinely complete sentences are joined together with just a single comma: "The character was afraid, she still walked into the house." The fix is usually simple — a period, a semicolon, or a coordinating conjunction like "but" or "and" after the comma. Reading a sentence and checking whether it contains two separate complete thoughts joined incorrectly is a quick, learnable check that catches one of the most common errors in student writing, and one that shows up in essays at every grade level.

A fast test is to check whether each half of the sentence, split at the comma, could stand alone as its own complete sentence. If both halves work independently, the comma alone isn't strong enough to join them, and one of the fixes above is needed.

Step 2: Fix Subject-Verb Agreement in Longer Sentences

Related: Better High School Writing - Essential Steps to Improve Now.

Subject-verb agreement mistakes usually happen when a long phrase sits between the subject and the verb, confusing which word the verb should match. "The list of items on the shelf were removed" is incorrect because "list," not "items," is the actual subject — it should be "was removed." Mentally stripping out the phrase between the subject and verb ("of items on the shelf") usually makes the correct verb form obvious.

This same trick works for sentences with compound subjects joined by "and" or "or," where students sometimes default to the wrong verb form out of habit. Reading the sentence with only the actual subject and verb left in, ignoring every descriptive phrase in between, is a fast and reliable way to check agreement in even the most complicated sentences.

Step 3: Untangle Misplaced and Dangling Modifiers

A modifier describes the word nearest to it, so placing it near the wrong word creates unintended and often confusing meanings: "Running down the street, the bus was missed by Maria" implies the bus was running down the street. The fix is to keep descriptive phrases directly next to the word they're meant to describe: "Running down the street, Maria missed the bus." This error is common because it doesn't always sound wrong when read quickly, so it helps to specifically check who or what each opening phrase is describing.

These errors are especially common in sentences that open with an "-ing" phrase, since it's easy to write the phrase first and then default to whatever noun comes naturally next, without checking that the noun is actually the one doing the action described.

Step 4: Keep Verb Tense Consistent Within a Passage

See also: Better High School Writing - Essential Steps to Improve.

Shifting between past and present tense within the same paragraph, without a clear reason, is a frequent and distracting error, especially in narrative or literary analysis writing. Deciding on a tense for a given type of writing — present tense is standard for discussing literature, past tense for narrating personal experience — and checking a draft specifically for unintended shifts prevents this issue from creeping in unnoticed.

A practical check is to circle every main verb in a paragraph and confirm they're all in the same tense family. Occasional shifts are sometimes necessary — describing an author's past life while analyzing their novel in present tense, for example — but those shifts should be deliberate choices, not accidental slips caught only by chance during a final read-through.

Step 5: Fix Pronoun Reference Problems

Pronouns like "it," "this," and "they" need a clear, single noun they're referring back to. A sentence like "The report criticized the policy, which surprised everyone" leaves ambiguous whether "which" refers to the report, the policy, or the criticism itself. Replacing a vague pronoun with the specific noun it's meant to represent, even if it makes the sentence slightly longer, usually improves clarity significantly.

This problem is easy to miss as the writer, because the intended meaning is obvious in the writer's own head — the ambiguity only becomes visible to someone reading the sentence without that context, which is exactly why it helps to read a draft as if seeing it for the first time.

Step 6: Build a Personal List of Repeated Mistakes

Most students make the same two or three grammar mistakes repeatedly across different essays, rather than making random new errors each time. Keeping a short personal list of the specific mistakes a teacher has flagged in past essays, and checking specifically for those patterns before submitting new work, is a far more efficient use of proofreading time than trying to catch every possible grammar error from scratch. This targeted approach — the same one used at Better High School Writing — turns grammar improvement into a specific, trackable process instead of a vague, ongoing worry. Over a few months of checking the same personal list on every essay, most students find that the mistake that used to show up constantly simply stops appearing, freeing up attention for the next one on the list.