Classes, students and certifications.
Add a course, schedule a class, sell a seat at the register, and run the class to the end. Three missions, about 20 minutes.
Add a course you teach, like Open Water Diver, with its agency, price and class size. Then schedule a class, the dates you run it, so students can join.
Open the class page, mark each student attending and then passed or failed, and close the class when it's done.
Enrol a student in a course and take payment in one sale. Put them in a class now, or enrol them and pick their class later.