The purpose of this project was to explore the decision-making approach and types of data that school psychologists use in determining special education classification. There were three research objectives: (a) to investigate the types of conditions and measures needed to test the use of the representativeness heuristic and assessment data, (b) to assess whether school psychologists use the representativeness heuristic and (c) to examine which types of assessment data are used by school psychologist when cases differ in complexity. Participants in Study 1 were 28 alumni from a graduate school psychology program, who were employed outside of Pennsylvania. In Study 2, participants were 272 school psychologists from the Association of School Psychologists of Pennsylvania (ASPP). All participants were certified in school psychology and had either a Master's or Doctoral degree. For both studies, a post-test only analogue design was used. Three student summaries, embedded with assessment data, were systematically manipulated to vary in complexity level (Learning Disability, Normal, and Complicated) and either randomly or systematically assigned to be reviewed by participants. The Decision-Making Questionnaire, developed by the author, was used to gather data about the use of the representativeness heuristic and assessment data by school psychologists. The representativeness heuristic was measured in four ways based on the research design of previous studies. Descriptive statistics, "t"-tests, contingency tables, ANOVAs, and MANOVAs with descriptive discriminant analysis were used to answer a total of eight research questions. Overall, findings suggested that the representativeness heuristic played a role in the decision-making of school psychologists, although depending on how it was measured, its use varied with the complexity of the student data summary. The findings also indicated that school psychologists were relatively consistent in rating the following data important in making eligibility decisions: achievement scores, IQ score, response-to-classroom modification, state criteria, and assessments of behavior. Additionally, focus on progress-monitoring data and referral information appears to influence the propensity to make classification errors. Lastly, the theory of bounded rationality is supported by results regarding the use of the representativeness heuristic and assessment data. Future research is needed to extend the generalizability of findings and to assess reliable ways of measuring heuristics. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]