What does the school's vocabulary change (teacher title, "form")?

The vocabulary only changes two things:

1. the help sentence "{Teachers} can validate {forms} and add stripes." in a student's progression and the Progression view of the attendance sheet;
2. the names of items created afterwards with "Use the starter template" (for example "Kata 1 — Basic stances").

Items already created are never renamed: rename them one by one in Progression if needed. Menus, buttons, the "Instructor" role and a class's "Instructor" field don't change. No title is placed in front of a person's name.

To change it: Settings › School › Vocabulary (owner), then Save. The plural is automatic (English: + s, consonant + y becomes ies).