How can the school see which parents and students are already registered?

Go to the web application. In the STUDENT, TEACHER AND CLASS MANAGEMENT you can see all the children created. The INFO column tells you if a parent, a child or both contacts are already registered. If the column is empty, no contact has been registered.

Registration codes that have not yet been redeemed are shown in black in the list. If the contact is already registered, the registration code is no longer displayed in the INFO column.