In his tweet, the boy stated that he was going to bring a bomb to school and blow it up, police said. He is now charged with disorderly conduct.
Winnetka Police found out about the tweet early March 6, and officers were able to confirm that there was no bomb within the morning.
"This is a very severe incident, and it's fortunate that it turned out there was no bomb," said Joe Pellus, Winnetka Deputy Chief of Police. "What I'd like to get out to the public is that words matter. Social media messages aren't private."
Pellus said teens should be aware that if someone reads a message with that appears to be threatening, they may very well take the matter seriously and report it to the police.
"This type of incident is similar to saying 'bomb' at the airport," he said. "It's going to be aggressively investigated."
The case has been referred to a peer jury.
Representatives from New Trier High School declined to comment on the incident.