Well, they don't necessarily have to show that scene. The movie might pick up from an adolescent Clark Kent, and move on from there. However if they were to explain it, I think Norminator79 has a good idea.
Originally Posted by Norminator79
good question. well i think the Kents may tell the police that they found him abandoned on the side of the road and would like to adopt him. Being it's a small town and the Kents have a good name they let them rise him as their own. i thinks thats would pass.