If you want to remove your school account from your Windows device or if you need to log into a different Office account, please follow the steps below:

• Click the start menu and search settings
• In setting select the Accounts tab on the left 
• Click on Access work or school
• Click the dropdown arrow to the right of the account name and select disconnect this account 

Now your school Office account should be disconnected from your computer and you can add your personal one if you need to.