I have heard of different reasons why Lansing was cut loose, from wanting more money or he didn't get along with the producer Quinn Martin from the start but found this article dated May 1965: Accordingly ABC has renewed 12 O' Clock High for another year - but Lansing will not be back. Reason: The show moves from the current 10:00 pm Friday slot, to the 7:30 Monday time slot next season to appeal to a younger audience. According to ABC top brass they wanted more physical action leading the group, like someone younger. Problem was Paul Burke was two years older than Lansing. Still another reason advanced was, "ABC does not feel the audience watching at that hour will identify with the lead character, a U.S. Air Force general. Consequently, Paul Burke has been signed on to star next season, playing a colonel." Yet when Quinn Martin offered Lansing the opportunity to remain with 12 O'Clock High next season, playing Paul Burke's wing commander, a character that would be of considerable dramatic importance but would appear only occasionally, Lansing refused. "That's not what made me bow out," Lansing said. "When I realized what changes would be made in the show for that younger audience, I knew that 12 O'Clock High couldn't be the same quality show next year, and 12 hours a day is too long to work at something you don't like." "I can't hate ABC," he says. "Hating a network would be like hating Dodger Stadium. Maybe I could be sore at the individual executive, but I have no idea who he is. My contract was with Quinn Martin, and he's the only man I've talked to. I can't be mad at Quinn either. He says it was the networks decision, and I have no evidence to make me doubt him."