I thought Peter had lighter colored hair also.
But now I recall he had streaks of gray hair, always combed long slightly over his forehead.
And now I found this to confirm my guess about his becoming Class 12:
"... Peter Buttery, Class 12 and OT8 was always sick, coughing up
phlegm and spitting it out in the trashcan, almost deaf, and late to arrive
Just need to dig up one of the Class 12 photos now.