WordBank Development Background

Using data from the Education Market Research report along with the top four best-selling textbook programs in the areas of science, math, social studies, and reading/ELA, the MetaMetrics’ Landscape of American Schools English Corpus was created.

The Lexile WordBank is an extension of the corpus that provides insight into how words are used in the corpus and where and when students are most likely to encounter them, and the overall level of challenge. Specifically, WordBank contains measures of word use, including word frequency by domain, grade, and bias and dispersion measures that describe how words are used across domains and textbooks as well measures to describe the complexity of the word.

Integral to WordBank are academic words. Academic words are used more frequently in textbooks or other academic contexts and not as frequently in oral language or narratives. Academic words can be general or domain-specific. Domain-specific academic words’ use is concentrated within a single domain (e.g., photosynthesis, quantity, or democracy) and general academic words are used across many domains (e.g., analyze, interpret, consequence).

Each word identified as a general or domain-specific academic word is assigned to a grade level where it is most instructionally relevant. To accomplish this, the relative volume of reading (total number of unique words at each grade) was first assessed. Then a corresponding number of the most frequently occurring academic words was assigned to each grade.

Additional word-usage metrics were calculated to provide quick insights into when and where each word is likely to be encountered by students. Based on a strong theoretical foundation of what constitutes academic vocabulary, the word-usage data contained in the WordBank, and input from literacy and vocabulary scholars, we developed a computational model of academic vocabulary. WordBank contains both a quantitative probability estimate from the model and a yes/no decision for whether each word is a general or domain-specific academic word.