The adoption approach made more sense to me than the above---far as the Langs/Chief Parker/etc. would be concerned, the Kents found an abandoned infant, took him to the authorities who could look for the infant's parents, said infant was offered for adoption by the Kents (once his parents couldn't be found), and the Kents took lil' Clark home. If one feels an orphanage is archaic (which I suppose it might be---assuming Kal-El landed on Earth in the mid-70s by this point in time), substitute "Smallville County Child Services" or whatever in its place. Seems more straightforward to me (and not asking us to accept some stupid-sounding snowstorm/Smallville having incompetent blizzard-handling skills/some improbable pregnancy...).
See, this is the exact problem I had with it too. Kents are honest, salt-of-the-earth-type folks. Why lie? Sure, omit the truth about the ship and all, but they'd do the right thing and turn him over to the police or appropriate community service organization. You know, for as apparently well thought up as the blizzard story goes, how do you think Martha would have handled the pregnancy lie when she took her regular gynocologist visit? Spooky...