Multiple Office 365 Accounts
You may experience problems logging multiple children into the same device/browser, should this happen then please try the following procedures.
If possible, use a different device for each child.
Do not choose the "Stay signed in" option when it is offered and log the first child out before attempting to sign the next one in. You may also need to close the browser to fully end the session before starting a new one.
Use a separate browser for each child. The most common to use are Chrome, Firefox, Opera, Edge and Safari (this last one is only for Apple devices, the others are available for both Windows and Apple).
Use a private browser session for each child. This will be named differently in each browser (not very helpful I know!) with Chrome and Opera it is "incognito", Edge uses "InPrivate", Firefox and Safari use "Private". This should work but do not select "Stay signed in" as above. To start a private session click on the menu button (at top right of most browsers) and you will find the option there.