Common Mistakes in Better High School Writing: Expert Advice on How to Avoid Them

Most high school essays lose points to the same handful of mistakes, repeated across thousands of students every year. Knowing exactly what those mistakes are makes them far easier to catch in your own writing before a teacher does.

A Thesis That Announces Instead of Argues

One of the most common mistakes is writing a thesis statement that simply announces a topic rather than making an actual argument. "This essay will discuss the causes of World War I" tells the reader what you plan to talk about, but it does not tell them what you claim about it. A stronger thesis takes a position: "Long-term alliance systems made a localized conflict in the Balkans escalate into a continent-wide war." The fix is simple but requires a mindset shift — after you draft a thesis, ask "so what?" If your thesis does not answer that question, it is a topic sentence in disguise, not an argument. A useful test: try writing the opposite of your thesis as a complete sentence. If the opposite version sounds equally reasonable, your original thesis is probably specific enough to be a genuine argument rather than a restatement of the obvious.

Evidence Without Explanation

Related: Better High School Writing - Best Practices for Stronger Communication.

A second frequent mistake is dropping a quote or fact into a paragraph and assuming it speaks for itself. Evidence never proves your point on its own — you have to explain the connection between the evidence and your claim. A quote from a novel followed immediately by a new paragraph, with no sentence explaining why that quote matters, leaves the reader to do the analytical work you were supposed to do. A reliable structure to avoid this: state your claim, present your evidence, then spend at least one full sentence explaining exactly how that evidence supports the claim before moving on. Skipping that explanation sentence is one of the single most common reasons strong evidence still earns a mediocre grade. A helpful phrase to build the habit: after any quote or piece of data, force yourself to write "this shows that..." or "this matters because..." before moving to your next sentence, even if you later revise the phrasing away.

Repeating the Same Point in Different Words

Many students pad essays to hit a word count by restating the same idea in slightly different phrasing across multiple sentences or even multiple paragraphs. This is easy to spot as a reader — and teachers spot it immediately — because the essay stops making forward progress. Before submitting, go paragraph by paragraph and ask whether each one introduces a genuinely new point or piece of evidence. If two paragraphs are essentially saying the same thing, combine them into one stronger paragraph and use the extra room to develop a point you have not made yet, or to add another piece of evidence instead of restating the first one.

Overusing the Passive Voice

See also: Better Writing Skills Checklist: Your Step-by-Step Guide.

"The experiment was conducted" and "mistakes were made" are grammatically correct but weaker than their active counterparts: "we conducted the experiment" and "the committee made mistakes." Passive voice is not always wrong — it is useful when the doer of an action is unknown or unimportant — but overusing it drains energy from writing and often hides who is actually responsible for an action, which is a particular problem in argumentative and historical essays. A quick way to check: search your draft for "was" and "were" followed by a past-tense verb, and for each instance, ask whether naming the actor directly would make the sentence stronger. Often it will. This matters most in argumentative and historical writing, where naming who did what is often the whole point of the analysis, and passive phrasing can accidentally let the actual subject of your sentence disappear.

Ignoring the Prompt's Specific Wording

A subtler mistake is writing a technically well-organized essay that does not actually answer the specific question asked. If a prompt asks you to "evaluate" an argument, but your essay only summarizes it, you have not completed the task, regardless of how polished the summary is. Common task verbs — analyze, evaluate, compare, argue, explain — each demand a different kind of essay, and mixing them up is a frequent, avoidable mistake. Before drafting, underline the task verb in the prompt and make sure your thesis and body paragraphs are doing that specific verb's job, not a related but different one. This single habit — underlining the verb before you write a word of the essay — is a small enough change that most students can start using it on the very next assignment without any real adjustment to how they already write.

Submitting Without a Second Read

The final and most avoidable mistake is treating the first complete draft as the finished product. Even fifteen minutes spent rereading a draft — checking that paragraphs flow logically, that your thesis is still accurate to what you actually argued, and that sentences are free of careless errors — catches a meaningful share of the mistakes above. Building this habit does not require a formal system; reading your work aloud, or running a short practice piece through structured exercises like those on Better High School Writing, trains the same self-editing instinct that eventually makes these common mistakes rare rather than routine in your writing. Most of these fixes take less time to apply than it took to read about them here — the real work is simply remembering to check for them consistently, essay after essay, until each check becomes automatic instead of an extra step you have to force yourself to remember.