To speed up Office 365 and make the experience smoother, some of the information is stored directly on your device.
1. More than one family member on a device can cause issues.
A. Consider using different browsers. e.g. one student in Chrome, and the other in Firefox
B. Using the private browsing mode or incognito mode in your browser so it forgets the other users
C. If you are using the Teams app, logout and then log back in again.