How can I update my biographical info?

In the top right-corner of the mySchoolApp interface, you can click on your name to reveal the drop-down menu and select "Profile": 

Your Contact Card will load up - this is what is shown in the school directory through mySchoolApp.

You can make changes to most of the fields by clicking on the "Edit" button, which appears like a pencil icon:

Proceed to make the desired change in the profile field and click on "Save" to commit the change to your profile.