Understanding and Evaluating Students with Disabilities
Evaluation as a decision-making process
Know the sequence: screening and pre-referral supports, referral, written parental consent, comprehensive multidisciplinary evaluation, eligibility determination, IEP development, and periodic reevaluation. Legally and professionally, teams gather multiple measures across settings and informants, using technically adequate instruments judged by reliability (consistency) and validity (measuring what is claimed). Understand how to read scores: most IQ and achievement tests use a mean of 100 and standard deviation of 15; percentile ranks describe standing in a normative sample; age- and grade-equivalent scores are easily misread and should not be used to describe performance.
Nondiscriminatory assessment
Evaluation must be conducted in the child's native language or mode of communication, free of cultural and linguistic bias, and may not rely on a single measure. A student cannot be found eligible based on lack of appropriate instruction or limited English proficiency. Distinguish difference from disorder: dialect features are not errors. Response to Intervention identifies risk and informs instruction; it does not by itself diagnose a specific learning disability.
Traps to watch
Percentile mistaken for percent correct; a single score treated as a precise point rather than a band around the standard error of measurement; reliability confused with validity; assumptions that a low IQ score automatically determines eligibility or placement.
Rule of thumb and example
Use multiple sources, settings, and informants, and report scores as ranges. A standard score of 85 with a standard error of measurement of 3 spans roughly 79 to 91 at two standard errors, overlapping the average range. Writing "85, low average, conclusively below peers" misuses the data.