Reading A-Z levels books uses the proprietary Learning A-Z Text Leveling System. This system takes into consideration three primary factors: qualitative measures of text complexity, quantitative measures of text complexity, and additional considerations pertaining to the reader and reading task that may influence the difficulty of the text.
The Learning A-Z Text Leveling System first considers qualitative measures of text complexity. These factors include the presence of, and the text dependence on, infographics. Additionally, the system considers the structure and organization of the text. Texts with a clear and logical structure and supportive labeling rate as easier than those without these reader-friendly features. The predictability of the text and the degree of prior knowledge necessary to comprehend the text also influence the final rating.
The quantitative measures of text complexity considered in this system are decidedly less subjective. These numerical considerations include the total word count and the number of different words present in the text. The system also considers several ratios, including the ratio of high-frequency words to total words and the ratio of different words to total words. Numerical valuations of sentence length and sentence complexity also impact the rating.
The final element of this classification system is the most subjective. This element requires the consideration of the potential reader and the required task. Because the impact of these elements varies from reader to reader and school to school, this component is not used to inform the letter difficulty the system assigns to a book, but is instead provided to teachers for their own professional consideration.