Asking students to write is one of the most difficult tasks we require. It tasks the writer with managing multiple cognitive functions all at one time: idea creation, organization, word choice, grammar rules, voice, correct sentences, and focusing on a topic. Whew. Writing this myself is taking a lot of hard work!
Because of the load that is placed on the writer, students are more successful when some of the individual tasks are broken down and isolated for them. Teachers do this in a variety of ways. We have them spell check at the end so they can focus on the ideas at the beginning. We have them review their sentences for run-ons or incompletion. We help them to organize in paragraphs. And most importantly, we try to help them with original and complete ideas.