Specific Learning Disorder 69
learning disorder. Evidence of persistent learning difficulties  may be derived from cumulative
school reports, portfolios of the child’s evalua ted work, curriculum-based measures, or clinical
interview. In adults, persistent difficulty refers  to ongoing difficulties in literacy or numeracy
skills that manifest during childhood or adol escence, as indicated by cumulative evidence
from school reports, evaluated portfo lios of work, or previous assessments.
A second key feature is that the individual’s performance of the affected academic skills is
well below average for age (Criterion B). One robust clinical indicator of difficulties learning
academic skills is low academic achievement for age or average achievement that is sustain-
able only by extraordinarily high levels of effort  or support. In children, the low academic skills
cause significant interference in school performance (as indicated by school reports and
teacher’s grades or ratings). Another clinical indicator, particularly in adults, is avoidance of
activities that require the academic skills. Also in adulthood, low academic  skills interfere with
occupational performance or everyday activities  requiring those skills (as indicated by self-re-
port or report by others). However, this criterion also requires psycho metric evidence from an
individually administered, psychometrically s ound and culturally appropriate test of aca-
demic achievement that is norm -referenced or criter ion-referenced. Academic skills are dis-
tributed along a continuum, so there is no natural cutpoint that can be used to differentiate
individuals with and without spec ific learning disorder. Thus, any threshold used to specify
what constitutes significantly low academic achi evement (e.g., academic skills well below age
expectation) is to a large extent arbitrary. Lo w achievement scores on one or more standard-
ized tests or subtests within an academic domain (i.e., at least 1.5 standard deviations [SD] be-