My HS had an electronics classroom since the late 60's, then the year after I graduated it was expanded to include 'Digital" - IC's & programming.
There was a computer lab but it was punch-tape terminals connected to a mainframe the other side of the country, with some in-house 'programming' by jumper wires on large breadboard sections that plugged in.
IMPO PLC's should be introduced in middle-school when kids are still open minded and learning and can ponder them in the back of their minds for years.