This dissertation comprises three complementary studies that aim to advance the understanding and practice of Individualized Education Programs (IEP) and Present Levels of Academic Achievement and Functional Performance (PLAAFP) development in special education. In the first study, we systematically reviewed empirical research measuring IEP quality, revealing heterogeneity in instruments used and a lack of standardized, replicated measures. In the second study, we established the reliability of scores obtained from a PLAAFP quality rubric, demonstrating strong interrater consistency (e.g., rank ICC = 0.91) and internal reliability (e.g., McDonald's [omega] = 0.82) through parametric and nonparametric analyses. In the third study, we investigated predictors of PLAAFP statement quality among graduate students. Results showed no significant impact of perceived school protocols but revealed improvements in PLAAFP scores after instruction (d = 0.59) and moderate social validity. Substantial variability across participants (45.1% ICC) and time points (10.1% ICC) highlighted individual differences and temporal dynamics influencing PLAAFP quality. Synthesizing findings across studies, key recommendations include: (a) replicating IEP quality measurement studies to accumulate reliability evidence; (b) establishing guidelines on sufficient reliability before implementing rubrics at scale; (c) emphasizing data skills in teacher preparation for composing high-quality IEPs; (d) exercising caution when standardizing IEP processes without reliability evidence. This dissertation provides a comprehensive examination of IEP and PLAAFP quality assessment, reliability, and determinants, informing teacher preparation practices and evidence-based policymaking to enhance educational outcomes for students with disabilities. [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.]