It is possible to take back or hide answers and feedback after they are mistakenly released to a student.
This can be done for individual students, whole classes and groups of students.
Take back an individual student's feedback and answers
Click the student's lesson in the Markbook and click Request resubmission. This will hide the answers from the student and allow them to continue working. Feedback will still be visible.
The page will refresh and reveal the Collect work button where the resubmission button was previously. Click this button to prevent the student from working on the lesson. Feedback and answers will both be hidden if the lesson is assessed.
Take back answers from a whole class
At the top of the lesson's column in the Markbook, click the ... button to access the Class controls menu. Click Request resubmission from all, and then click Collect all unfinished work.
Take back answers for a group of students
Use the Markbook filters at the top left of the page to select which students' work you want to control, and then click the ... button at the top of the lesson's column to access the Class controls. Click Request resubmission from all, and then click Collect all unfinished work. Using these Class controls in conjunction with the Markbook filters means only those students visible will be affected by the Class controls.
The teacher can also hide the lesson from the class via the Differentiation controls on the Lessons page if marking is complete and other classes are still working on the lesson. Students will still get a note in their Notifications menu that feedback has been released, but clicking the link in the notification will result in a Permission denied page.