Today Apple released an update to iOS 9. MClass has released this statement regarding the update:
IMPORTANT! iOS 9 Update On Wednesday, September 16, Apple is releasing its new operating system, iOS 9. mCLASS® assessments are compatible and ready for use with iOS 9, with the exception of mCLASS Beacon and mCLASS:TPRI.
All mCLASS products will continue to work on iOS 8, as well.
Warning: Users upgrading their Apple devices to iOS 9 must sync the mCLASS app before upgrading to avoid losing data stored on the device.
The Team at Amplify
I would have your teachers carefully look at the amount of space they have available on their device prior to updating. This update takes 1.3 GB and the last update was 4.6 GB so if they are still at iOS7 they will need 5.9 GB free to upgrade to the most current iOS and this is almost 1/2 of the storage on the devices.