When a child first logs into the platform, they will be greeted by their teacher at the top with an optional welcome message which can be added in via the Class Homepage editor. To ensure that the right member of staff is showing, you will need to log in as an administrator and navigate to CP > Classes. From there, please click on the class name and choose the Main User tab. 

From there, you can then tick the radio button next to the class teacher in question and press finish to save changes. The next time a pupil logs in, they will then see that member of staff display on their Dashboard.