There is barely a school in the country in which the "outcasts" - computer nerds, punks and other eccentrics bearing even a superficial similarity to the two Littleton gunmen - have not been eyed suspiciously. Their tastes in music, video games and even their clothing have come underscrutiny, and every remark carrying a hint of aggression has been reported to the authorities.
One student in Irvine, southern California, who told a classmate: "I wish you weren't here," was reported to his principal for making death threats. Another southern Californian schoolboy, David Hancock of Glendora High, has been suspended for continuing to turn up to school in his favourite trench coat - the item worn by Eric Harris and Dylan Klebold during their rampage in Littleton in which they allegedly killed 12 students and a teacher at Columbine high school before shooting themselves.
Five students at a middle school in Brooklyn, New York, have been expelled after they were overheard talking about blowing up their school. A 12- year-old who made a similar boast in Pasadena, California, was arrested, even though police found no evidence that he had the means to carry out the threat.
With parents understandably jumpy about their children's safety, every rumour on the Internet or in school corridors has been blown up to panic proportions. Extra police, some with sniffer dogs and other bomb-detection paraphernalia, have been drafted to check lockers and cupboards at schools across the country.
The biggest scare came last Friday, the 54th anniversary of Adolf Hitler's suicide which had been trumpeted on the Internet as a "day of judgement", echoing the decision by Harris and Klebold to attack their school on Hitler's birthday, 20 April. School districts reported absenteeism as high as 40 per cent.
"This is a terrible time for school administrators, teachers and especially students and parents," said John Lammel of the National Association of Secondary School Principals. "You have to give every phone call, fight and bomb threat even more serious attention than usual. It sets everybody in a very high state of nervous energy."
Some of the threats have been truly menacing. A mother of a student in Arvada, Colorado, with a history of confrontation with the school administration was arrested after leaving this message on an answering machine: "There goes your students. There goes your school. This is not a joke." The premises were evacuated while police spent two hours searching for bombs. Nothing turned up.
Evidence of imminent violence has been rare. The one serious incident occurred in Canada, where a 14-year-old opened fire in a high school last week, killing one student and seriously injuring another.
Five 14-year-olds were arrested a week ago in a suburb of Austin, Texas, after bombs were found at their homes. A teenager in Oxnard, California, was arrested over the weekend after he was caught with 10 pipe bombs.
Since the Littleton massacre, the whole country has been anxiously searching for answers to the question: why? The National Rifle Association, which faced thousands of protesters as it went ahead with its annual meeting in Denver at the weekend, has sought to blame youth culture and poor parenting.Reuse content