I used to pick up out-of-market TV Guides at their office in
Dallas, and I seem to remember before we left there in '79 seeing an
ad in the Central Indiana edition concerning WTHR's switch
to NBC: "We've graduated. We've mastered our ABCs. Now
we're graduating to NBC." When did the WRTV/WTHR switch
take place?
According to Wikipedia, the swap took place June 1, 1979. Considering NBC's fortunes at the time, it seemed more like a demotion for WTHR rather than a "graduation". However, over the years, WTHR became Indy's top station while with NBC.