ALLERTON - A young Bronx boy has been reunited with his parents after wandering from his kindergarten yesterday afternoon. The parents of 6-year-old EJ Rodriguez say he left his classroom at P.S. 96 without anyone noticing and walked three blocks to his baby sitter's house. His mother, Aisha Melendez, says she couldn't find him at the end of the school day, and that she thought he might have been kidnapped or struck by a car. The principal says the incident is under investigation.