A third grade essay should detail the writer's opinion, not summarize or describe a topic. Furthermore, students should pick one side of an issue, rather than waffling back and forth or sitting on the fence and saying both viewpoints are good or that they don't know which one is better. A proper essay states its opinion in one clear and easy-to-understand sentence.
Third grade writers need to demonstrate the validity of their arguments by supporting them with evidence in the form of examples and details. The evidence may not be persuasive enough for an adult reader; more importantly, teachers should mark students for attempting to explain their beliefs or opinions. Answering "why" encourages students to reflect on their ideas -- the first step in critical thinking.
Students in grade three are usually too young to construct standard paragraphs. However, young students need and should learn to follow some kind of format for their essays. Expecting students to create a title, state their opinion sentence near the beginning and end with a concluding statement is reasonable. Teachers should provide students with a model essay outline to help them organize their ideas. One learning objective of writing an essay in grade three is memorizing and internalizing proper essay format. Another option for formatting is allowing students to supplement the essay with an illustration, title page or other creative element.
In grade three, many students have not mastered sentence structure, punctuation and spelling. This makes marking a third grade essay tricky, as teachers will have to overlook some mechanical errors. Essays that display an essential understanding of language structure and are able to communicate ideas relatively clearly, regardless of language errors, deserve reasonable marks.