The report finds that Noel Estevez was not bullied or harassed by victim Timothy Crump on school grounds in Mount Hope, but it does not rule out that bullying took place elsewhere.
Estevez's attorney says the June stabbing was in self-defense after months of bullying by Crump.
Estevez is charged with second-degree murder and manslaughter. Prosecutors read part of his confession during his arraignment in court.
"The kid kept hitting me with his fists, so I pulled a knife and stabbed him four or five times," he reportedly told officers.
Officials say Crump was actually kicked out of school on December 16 for punching another student, but was often seen hanging near the building.
Estevez had just returned to school after being hospitalized following a suicide attempt. His father asked for a safety transfer but was denied because it was so late in the school year.
"Here's a child being threatened," attorney Eric Poulson said. "People coming to his door, continually, saying we're going to kill you. You're dead. They were after him for three months. They couldn't find him because he stayed behind closed doors. He came out of closed doors, and they sicced on him."