The (Peoria) Journal Star reports the boy told friends he was frustrated with being picked on and bullied and was going to shoot students at Farmington High School.
During a juvenile court hearing Friday, a prosecutor read from a statement the teen gave police. In it, he said the threats were a "dumb idea" and that he didn't plan to carry them out.
His attorney said students interviewed by police didn't believe the teen was serious.
The teen faces probation when he is sentenced Feb. 1. A judge also ordered a psychological and drug and alcohol evaluation.