NSW teenage boy charged for IS threats

A teenage boy who screamed death threats against Christians outside a school in Sydney's west has been charged.

The 14-year-old was in the front passenger seat of a red hatchback driven by another man when he allegedly began bellowing abuse outside the Maronite College of the Holy Family in Harris Park on September 16.

Onlookers told AAP they threatened to "kill the Christians" and slaughter their children while brandishing an Islamic State flag.

College spokesman Joseph Wakim told Fairfax Media at the time the school community was shocked but stressed no students were around when the threats were made and the incident was an isolated one.

Following an investigation, the teenager was arrested by police on Tuesday.

He was later charged with intimidating a school staff member and offensive conduct.

The boy will front a children's court on October 13.