If your school has a zero cell phone policy, you can prevent students from signing in with their mobile phones by following this guide.
Video Walkthrough
How to Turn Off/Turn On Mobile Device Access
From the admin view, click Rooms.
Click "Options" at the top right of the Rooms page.
Toggle off "Allow students to use phones" to disable students from signing in with their mobile devices.
Click Save.
When a student tries to sign in on a mobile device, this is what will show on their screen:
FAQ
Can students still access their student IDs with mobile devices being disabled?
Yes. Students can still access their student IDs even if mobile devices are disabled.
What are considered mobile devices?
This feature prevents students from signing in using an iPhone, iPod Touch, and Android phones (both app and web browser). Logging in using iPads, laptops, or computers is still allowed.