I graduated from high school in 1969. I remember discussing continental drift in high school physical science class (1967 in a small rural high school in Pennsylvania}. It was in the earth science text I used to teach ninth graders in 1973 - and it was by no means a new textbook - at least 5 years old. So anyone who graduated from high school after 1970 should certainly have been exposed to the concept.
Edited by deerbreh, : No reason given.