When did Superman tell Superboy his secret identity?
Superman's secret identity
it was in the sins of youth story where the ages of all the Dc adult heroes were switched with the teen heroes, Supes needed Superboy to cover for him with Lois and had his dress up as Clark Kent cause they looked similar but he stayed at a distance so Lois wouldn't find out
Course I may be wrong on this since it's been years since I read the story.
What I was thinking of was where kon-el went to the kent farm and was hinting to clark he knew his identity and clark hinted back that it was true, but your right he doesn't outright reveal it until sins of youth.
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