Requesting revisions for every student can seem like a daunting task if you did this student by student. You can actually set the whole class to Request Revisions mode in the Grade By Question view.
#1. Access the Grade by Question page of the activity by clicking on the activity title, then clicking Grade by Question in the upper-righthand corner.
#2. Select ANY question to grade by putting a check in the box next to the question, then scroll to the bottom and select Grade Questions.
Pro tip: Longer assignment? Ctrl+End on your keyboard will zoom you to the bottom of the page.
#3: While on the Question page, scroll to the bottom. There is an arrow next to Save All. Click on the arrow and select Request Revisions. This will change all students to the request revisions status. You will see their grading progress change, and you will get a green notification that your task was successful.