Choose a topic suitable for third grade, such as what changes you would make in the school lunch room, why it is important to learn to read, or what animal you would choose for a class pet and why. Do some appropriate research and make a list of points you wish to address. Whatever topic you choose, it should be narrow enough to be covered adequately in a four or five paragraph essay.
Write out the introduction to your essay that explains what you will be discussing in the essay's body. Include a thesis statement, which should be narrow and defined enough to be supported within the essay. The thesis statement must also express the essence of the essay, which will then be developed and supported in the paragraphs of the essay's body.
Write two or three paragraphs that will make up the essay body. Support the claims you make in your introduction, and make sure to discuss only one or two points per paragraph. This keeps the essay concise and ensures it follows a logical progression. Refrain from putting too much emotion or opinion into the essay. Instead, focus on facts and stay objective.
Write a conclusion that restates the thesis and provides a summery of the information you have presented.