I tried spaced repetition in the classroom for years in many different ways. I showed SuperMemo to some students who seemed self-motivated to work alone. I used ad hoc repeat quizzes with the whole class (i.e. not on a special schedule, but when I felt like it might boost their memory). I created more formal schedules for myself to systematically return to previous topics and build on them with the whole class. And finally I wrote my own spaced repetition software from scratch.
From these efforts my conclusion was that spaced repetition does embed memories, but to be sure they are good memories the student must be in control. By "good" memories I mean ones that add to the student's understanding, which open their eyes to the world rather than just assisting them to gain an extra test mark. Otherwise, those students just became proverbial parrots of my knowledge.