The externalizing scale of the YSR/ASR consists of 30 items comprising both rule-breaking (e.g., ‘I cut classes or skip school’) and aggression items (e.g., ‘I am mean to others’), for which the participant indicates whether the behavior is not true, somewhat or sometimes true, or very or often true (Achenbach, 1991, 1997). These measures have been shown to have excellent psychometric properties including high test–retest reliability, content validity, criterion-related validity, and construct validity (Achenbach & Rescorla, 2001, 2003).
