A study of school effectiveness for language minority students, authored by Virginia Collier and Wayne Thomas, is criticized as having two serious flaws. The first is that its methodology is a simple descriptive cohort analysis, seen as unscientific and producing misleading results because: each grade consists of different students; the number of students in each grade is not given; there is no statistical control for pretreatment differences; and the test scores shown after elementary school are not for the same cohorts. The second flaw is that little about the methodology is explained. (Contains 14 references.) (MSE)