1 · The new year
Promotion moves students into a new academic year. Last year is kept untouched as history.
Current year: …
2 · Promote a class
Review one class at a time. Each student's next class is proposed; adjust any, then promote.
Set all to:
3 · Start the new year
When every class has been promoted and you're ready for the new term, switch the school over.
This makes the new year the current one: marks entry, class lists and documents will then use the new year. Do this only once all classes are promoted.