English as a subject is full of topics you can teach a short, single class on. All you need to do is consider the various options and decide what will work and what is too complicated to be made into a short topic.

Short Stories

As a rule, creative writing tends to be a topic that will catch students' interest because it allows them to let their minds roam free. They don't have to follow strict rules, as they would with grammar or spelling exercises. Explaining what a short story is to the class, followed by reading an example of a three- to five-page story, should lay out the basics. By the end, students should know when a short story becomes a novella, and students should be allowed to write their own story as an assignment over the course of a few days or a week.

Purpose of Essays

While essay writing is a large part of high school and college English, it's important before you start assigning page counts and subject requirements that you explain to your students just what the purpose of writing an essay is and how the students can fulfill that. An essay can be written to inform, persuade or entertain, and sometimes those purposes can be mixed. Show students that your essay has to take a certain view; otherwise your essay might become meandering and confusing. Point out that you can persuade while being informative if you make your arguments clearly, or that you can be entertaining while you persuade by writing in a fun or comical manner.

Haiku

Haiku are a major form of verse in Japan. These poems have a 5-7-5 syllable requirement. They're never more than that, with each number being one line of the haiku. You can make this a cultural lesson as well as an English lesson to keep the students' interest. For instance, come to class dressed in a kimono and read some traditional haiku. Or you could bring some more modern examples, such as reading from the book of Zombie Haiku. The offbeat nature will make the lesson stick, and it doesn't need to last more than a single session.

The Speaking-Writing Connection

It's an adage that people who speak properly will write properly. Since speech is the main medium through which people communicate, point out that the style of English a student uses is reflected in his writing. This lesson might help students realize some problems they're having with expressing their thoughts and views. If their speaking can be corrected, it will make writing a great deal easier.