Eleven students were arrested after a knife fight broke out just before noon at John F. Kennedy High School in Waterbury. Police said nine boys and two girls under the age of 18 were charged with third-degree assault, second-degree breach of peace, and interfering with an officer. Several students were hurt, but none seriously. The school nurse treated all injuries. A school resource officer, with help from local police, broke up the fight. Investigators have not said what led to the violence.