For over a half-century elementary school teachers have organized students for reading instruction into achievement groupings (sometimes mislabeled "ability groups"). The traditional three group scheme-top, middle and bottom-was recommended shortly after the turn of the century as a better alternative to whole class instruction. The three group scheme has come under increasing scrutiny over the past few years as American society changed and our understanding of how children learn to read and write increased.
Allington, R. L. (1992). Reconsidering Instructional Groupings. Reading Horizons, 32 (5). Retrieved from http://scholarworks.wmich.edu/reading_horizons/vol32/iss5/2