“…Elevated levels of externalizing behavior (e.g., aggression, oppositional behavior, disobedience) in the early years of life forecasts a variety of problems later in childhood (Campbell et al., ). Left untreated, externalizing behavior often worsens with age and tends to persist over time (Mesman, Bongers, & Koot, ; Vaughn, Salas‐wright, Delisi, & Maynard, ), generating substantial social and economic costs to individuals and society (Raaijmakers, Posthumus, Van Hout, Van Engeland, & Matthys, ; Scott, Knapp, Henderson, & Maughan, ). These observations underscore the importance of early intervention to ameliorate such early emerging problems.…”