When Jack Knight and Mikaal are sent back in time, and they visit Krypton before it exploded, Jack immediately recognizes Jor-El as "Superman's dad" based on his name alone. Now, Jack is hardly pals with Supes, so is Superman's planet of birth and his ancestry supposed to be common knowledge?
At this point in the DC Universe it's pretty common knowledge that Superman is Kal-El and from the planet Krypton.
More specifically, in the Post-Crisis universe, Superman gives an interview to Lois Lane sometime just after Man of Steel #6 in which he reveals all of this, and later stories have news media or footage that would show things like the Jor-El statue in his Fortress and so on.
