Purpose: Spelling is a critical component of literacy and language arts that can negatively influence other aspects of written composition. This clinical focus article describes a spelling error classification system that can be used to identify underlying linguistic deficits that contribute to students' spelling errors. The system is designed to take advantage of the linguistic expertise of speech-language pathologists to efficiently assess student errors in written compositions that are generated as a component of everyday classroom instruction. Method: A review of the literature was conducted regarding spelling as a component of literacy and language arts, the development of spelling, and the linguistic contributions to spelling. Then, existing criterion-referenced measures of spelling simple and morphologically complex words were reviewed, and a new, manual technique for analyzing spelling in student written compositions was created. Conclusions: The language expertise of speech-language pathologists enables them to readily evaluate the phonological, orthographic, and morphological errors in student misspellings, in order to identify specific underlying linguistic deficits and plan targeted interventions. The error classification system provides speech-language pathologists with a tool that is both simple and time efficient and, thus, may help increase their confidence and ability in addressing the spelling needs of students.