Common Core Standards
Grade 3
Writing W.3.10
Write routinely over extended time frames (time for research, reflection, and revision) and shorter time frames (a single sitting or a day or two) for a range of discipline-specific tasks, purposes, and audiences.
Write early and often. But this standard wants you to mix it up. Rather than the same old stuff everyday, give students different types of writing with different length requirements. This will build a variety of writing skills for students.