They are only looking for these things:
· Well-focused main points (pick an idea and stick to it, don't ramble)
· Clear organization (five paragraphs: Introduction, three supporting paragraphs, and your closing which basically restates what you said in the introduction)
· Specific development of your ideas (make your three paragraphs match what you said in the first paragraph)
· Control of sentence structure, punctuation, grammar, word choice and spelling
They may assign a topic depending on where you live, or it may be left up to you to choose a topic. (more likely)
Go ahead now and pick a topic and develop the essay so when the day comes and you have to write it, you'll already know what you need to say.
The basic idea of an essay is that you're going to 1. Ask a question 2. Answer the question and explain why you think your answer is right.
So try something like "Should students be allowed to grade their teachers and why or why not?" You don't have to make both arguments, just pick the answer you think is right and go from there.