Student getting around guided access

Devices with a physical Home Button

The way to get out of Guided Access without the associated Passcode is to press the Home and Power button together for 15 seconds. This will turn off Guided Access by forcibly rebooting the device. Once the device is restarted, you can then go to Settings > Accessibility > Guided Access > Guided Access - and turn off Guided Access.

Use Guided Access on iPad - Apple Support

Use Guided Access with iPhone, iPad, and iPod touch - Apple Support

Devices without a physical Home Button

For iPad’s without a physical Home button, you follow a slightly different button sequence…

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

After restart:

Settings > Accessibility > Guided Access > Guided Access - turn off Guided Access.

Unless your student's iPads are centrally managed by an MDM system - and a restrictive policy applied - your only opportunity to restrict access to Apps and features would be ScreenTime or Parental Control restrictions.

Set up Screen Time on iPad - Apple Support

Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support

You're very welcome.