View and lock a student’s screen with Classroom
You can control how and when students can use their Mac — including sharing files or viewing their screen — to make sure they stay on task. When you view a student’s screen, the status bar on their Mac turns blue.
Note: Depending on how your mobile device management (MDM) solution is configured, you may not be able to perform this task. Contact your MDM administrator and have them review Manage AirPlay and screen view settings in MDM.
View the student’s screen
Open the Classroom app
on your Mac, then select the student.Click Screens in the toolbar, then double-click on the student’s screen to view it.
To view the screens for more than one student, see View the students’ screens.
Lock or unlock the student’s screen
You can prevent a student from using their device by locking it. Locking a student’s device also requires that students enter their passcode or password after the screen is unlocked.
Open the Classroom app
on your Mac, then select the student.Click Lock
in the toolbar to lock the screen or click Unlock 
to unlock the screen, then click Done.
To lock or unlock the screen for more than one student, see Lock students’ screens and Unlock students’ screens.