Many text-leveling systems in the early grades rely on holistic, subjective human judgments that are the result of individuals going through a training program to learn to apply the leveling system. Fountas & Pinnell’s Text Level Gradient is an example of such a framework. It involves trained individuals independently reviewing and assigning a level to the texts (e.g., A, B, C) based on text characteristics such as word familiarity, sentence complexity and format features. Then, through a group consensus process, they assign a single level to each text.
The Lexile studies of early-reading texts also involved expert judgment; however those judgments were validated with empirical student performance data on the same texts and the judgment decisions were anchored to a quantitative developmental scale — the Lexile scale — appropriate for assessing the complexity of texts from kindergarten to college. Additionally, because Lexile text measures are calculated by a machine (i.e., the Lexile Analyzer), they can be a scaleable solution by being quickly and reliably produced for large collections of texts.
Since the methods used to determine the complexity of texts varies across the different leveling systems, the complexity levels assigned to the texts may also vary. As a result, there is not a direct correspondence between a specific Lexile measure for a text and a level from another system (e.g., Fountas & Pinnell’s Guided Reading Levels), although there is typically a high degree of correlation in the order in which books appear in the various systems. In other words, texts receiving a low Lexile measure typically appear in the low levels of other systems.