A 9-year-old male in third grade is referred by his pediatrician for psychiatric evaluation due to behavioral problems at school. His teacher reports that he is disruptive, frequently out of his seat, and does not complete assignments. His parents report that homework takes 3-4 hours nightly with constant supervision. Vanderbilt ADHD rating scales completed by parents and teachers are positive for ADHD, predominantly inattentive presentation. However, review of his academic records reveals that while he excels in mathematics and science, his reading comprehension is at a first-grade level despite average intellectual ability documented on prior psychoeducational testing. He had speech-language delays as a toddler but was discharged from speech therapy at age 5. He becomes frustrated and tearful specifically during reading-based tasks. What is the MOST important diagnostic consideration?