“…There are two lines of evidence that support this explanation. First, behavior disorder is associated with classroom underachievement (Pardini & Fite, 2010;Timmermans, van Lier, & Koot, 2009) and thus may also lead to underachievement on IQ tests. Second, behavior disorder is associated to school drop-out rates (Porche, Fortuna, Lin, & Alegria, 2011) and drop-out rate is associated to subsequent deterioration of verbal skills (Vaughn, Beaver, Wexler, DeLisi, & Roberts, 2010), possibly lowering verbal IQ.…”