Can I track progression without creating a curriculum?

Yes. A curriculum is optional. Without one you can still write notes and milestones.

1. Open a class's attendance sheet, Progression view, and tap Note: without a curriculum, the card shows only the last note.
2. Choose Just a note, write the note (required in that case), tap Save.
3. Or, in the student's progression screen, Add a note or Add a milestone.

These notes go into the student's Journal, without a curriculum. Only the owner creates a curriculum, if the school wants one later (Progression > Add a curriculum).