I don't see any point in graduation, really. Why stop learning? The ideal school curriculum, in my mind, would have four unassisted co-op terms (i.e. two years of real, normal work) followed by one or two terms of instruction, repeated in a cycle, for as long as you may live. At no point would you be handed a certificate and kicked out of the building; you'd just keep coming back and learning more stuff (presumably in a myriad of unrelated subjects), then going back out and making use of it.