7 Common English Grammar Mistakes Students Make (And How to Fix Them)
Published 1 June 2026
Writing a good essay takes practice, and grammar is one of the trickiest parts. Even students who read a lot can fall into the same patterns of error again and again. Here are the seven most common grammar mistakes found in school essays — with clear explanations and practical tips for fixing them.
1. Subject-Verb Agreement
This happens when the verb doesn’t match the subject in number. Singular subjects need singular verbs; plural subjects need plural verbs.
Wrong: The list of items are on the table. Right: The list of items is on the table.
The subject is “list” (singular), not “items.” When a phrase comes between the subject and verb, it’s easy to be confused. Always identify the real subject first, then choose the right verb.
Tip: Underline the subject in your sentence before choosing the verb form.
2. Tense Consistency
Jumping between past and present tense in the same piece of writing is one of the most common problems in student essays.
Wrong: She walked into the room and sees a cat. Right: She walked into the room and saw a cat.
Pick a tense and stay with it throughout your essay, unless you’re deliberately referring to something that happened at a different time.
Tip: Before finishing your essay, read through it once and only focus on tenses. Underline every verb and check they all match.
3. Missing Articles (a, an, the)
English uses articles in ways that don’t directly translate from Chinese or other languages. This is one of the most common errors for students whose first language is not English.
Wrong: I saw dog in the park. Right: I saw a dog in the park.
Use a or an when you mention something for the first time or when it’s one of many. Use the when you’re referring to something specific that both the writer and reader know about.
Tip: Read your sentences out loud. If something sounds like it’s missing a word before the noun, you probably need an article.
4. Run-On Sentences
A run-on sentence happens when two or more complete sentences are joined together without proper punctuation or connectors.
Wrong: I went to the shop it was closed I went home. Right: I went to the shop, but it was closed, so I went home.
The fix is to either split the sentence into two, or use a conjunction like and, but, so, or because to join them properly.
Tip: Look for long sentences. If a sentence goes on for more than two or three ideas, check whether it needs a full stop or a proper connector.
5. Comma Splices
A comma splice happens when two complete sentences are joined with only a comma instead of a conjunction or a full stop.
Wrong: It was raining, we stayed inside. Right: It was raining, so we stayed inside. or It was raining. We stayed inside.
A comma alone is not strong enough to join two independent clauses. You need a conjunction (and, but, so, yet, for, nor, or) or a semicolon.
Tip: If you can replace the comma with a full stop and both halves make sense on their own, you probably have a comma splice.
6. Incorrect Prepositions
Prepositions are small words like in, on, at, by, and to — but they follow rules that are hard to explain and have to be learned through exposure.
Wrong: I am interested on history. Right: I am interested in history.
Wrong: She arrived to the airport. Right: She arrived at the airport.
Tip: When you learn a new phrase or expression, learn the preposition that goes with it as part of the phrase — don’t try to translate from your first language.
7. Capitalisation Errors
In English, certain words are always capitalised: the first word of a sentence, names of people and places, days of the week, months, and the word “I.”
Wrong: i visited london last monday with my friend james. Right: I visited London last Monday with my friend James.
However, school subjects like maths or science are not capitalised unless they are part of a specific course title.
Tip: After writing a sentence, check that it starts with a capital letter. Then scan for names, places, and the pronoun “I.”
Improving your grammar takes time, but the most effective way to get better is to review your own writing regularly. When you get an essay back from your teacher, look carefully at the corrections — don’t just note the mark. Understanding why something was wrong is how you stop making the same mistake next time.
GrammarEasy can help you spot these kinds of errors instantly, with clear explanations so you understand the reason behind each correction.