Learning to read is a personal journey experienced in a socio-emotional context. It requires exposure, instruction, interaction, interest, and time. Some children learn before formal school instruction, often in homes that provide rich language and literacy environments. Normative expectations are based on what the hypothetical average student can achieve, and children are compared to peers of the same age or grade. Reading is a complex activity relying on the coordination of areas such as motor, perceptual, cognitive, and linguistic processing. While the trajectories of struggling students are the focus of this chapter, it is important to acknowledge that all children experience variability in learning, with some skills consolidating with more ease and speed, and others more prone to external influences that facilitate or inhibit progress. Reading comprehension impairment is distinct from dyslexia, and, in comparison, under-recognized. The definitions of reading disabilities are not based on data related to brain structure or function.