You may have noticed that Windows will remember by default the last logged-in user. This is supposed to be a convenience, but when you have a lot of users sharing computers, it will often add an extra step to have to click Switch User before entering a username and password.
There are two ways to disable this.
One way is through the registry. If you hit Windows-R and type regedit you will launch up the registry editor.
Navigate to HKEY_LOCAL_MACHINE > Software > Microsoft > Windows > CurrentVersion > Policies > System
Double-click dontdisplaylastusername and then change the 0 to 1
Alternatively, if you want to change it through Group Policy, you can hit Windows-R and type gpedit.msc which will launch up the Group Policy editor.
Go to Windows Settings > Security Settings > Local Policies > Security Options
Then double-click Interactive logon: Do not display last user name and change it from Disabled to Enabled
Then, you should no longer see the last logged-on user at the login screen.