Harris and Kleblod made a class video in which they conducted a mock attack on the school. Klebold wrote essays with violent themes in English class. Harris maintained a Web page in which he posted his hate-filled ravings. And both teens' expressed a fascination with Hitler and expressed an intolerance for blacks, athletes, disabled people and others.

The FBI study also listed school, social and family dynamics that should be considered, including an acceptance of pathological behavior by parents, unsupervised access to weapons and the Internet, the existence of an "inflexible culture" or the development of unfair disciplinary structure.

Jefferson County school officials, some of whom participated in a symposium that contributed to the report, reviewed the document.

"Pieces of the report confirm much of the information that (Columbine principal) Frank DeAngelis shared with the review commission," spokesman Rick Kaufman said. "Our formal threat assessment policy is certainly consistent with the FBI model."

But Kaufman repeated the district's position that there was no way to predict the violence.

"We are pretty confident that if there were signs exhibited by Eric and Dylan or examples of an imminent threat, we would have responded," Kaufman said.

"There are many individuals who may exhibit tendencies but would never pull this off."

Others expressed similar concerns. Vincent Schiraldi, a children's advocate with the Justice Policy Institute in Washington, said he worries the report will be used to label otherwise typical students as potential killers.

"I think this opens the door for a tremendous amount of false positives," Schiraldi said. "The ramifications for kids being misidentified as dangerous would be huge.

"Frankly, I see no role for the FBI in America's schools."

The FBI report recommends that school officials consider the personality traits only after a threat has been reported. The threats could be direct, indirect, veiled or conditional.

The type of threat is key to determining how it should be handled. A high-level threat, defined as one that is direct, specific and plausible or comes with evidence that steps have been carried out, almost always requires "immediate law enforcement intervention," the report said.

Attorney General Janet Reno acknowledged that "the risk of unfairly stigmatizing children is great," but said the threat assessment model, if applied judiciously, will have a positive impact.

"We will be in a position to help those children who show a propensity for violence, before they scar themselves (and others) forever," Reno said. "And we will be in a position to protect innocent school children before they become senseless victims."

The Houston Chronicle contributed to this report.