You can control when students review their assignments when you create the assignment. In Step 1, in the "Release for Review" section, you can choose "On Submission" or "By Teacher." If you want students to automatically review their assignments, leave the default selection of "On Submission," and students will be able to review their assignment as soon as they submit it. If you want to manually release the assignment for review, select "By Teacher."  Once you are ready to release the assignment for review, click "Release Review" for that assignment on the Reports page.