Each school chooses a secret key when the account is setup. Only teachers who need it are told the key.
It is impossible to read the names without the key.
So, only teachers from the school, logged in to the app and who know the Secure Key can decrypt student names (inside the dotted box).
Reminder: You should avoid sharing the Secure Key via email.
Your email account and the Secure Key are both needed for a third part to access identifiable data.
Keeping the Secure Key separate makes this more difficult.
With emails, one-way encryption is used to make it impossible to decode them, but still be used to confirm identity.