Superman takes Batman back in time to Krypton before its destruction in the Bates, Andru and Esposito story in World’s Finest 191 (Feb. 70).
The story opens as Superman and Batman are summoned to a secret government installation, and see Jor-El and Lara there. The couple disappear, and the general who called on the heroes is now in a coma. Figuring these events to be related, Superman heads back to Krypton, bringing Batman with him.
There, we see university protests, much like the ones in the US at the time. Is this a warning that the end of times is coming for planet Earth? Nope, not really. But it does give the heroes the opportunity to go into action, and get noticed by Jor-El and Lara. Curiously, this story gives Jor-El only the haziest memory of having known Superman in his previous time trips to Krypton.
Superman and Batman tail Jor-El and Lara, and find that they are running a secret crime school. Superman is appalled, but the two join it anyway, planning to turn Superman’s parents in when they have proof of their crimes.
As it turns out, the crime school existed simply to train students to infiltrate a criminal world, in an attempt to retrieve what is believed to be a former Kryptonian god. The ending of the story stretches things a lot, and overall the tale is a bit of a disappointment, with too many dangling plot threads.