Ten algorithms for measuring school effectiveness were identified through literature analysis and interviews of the directors of 39 school improvement projects. The algorithms are described thus: (1) a major proportion of students achieve at or above average national levels; (2) an equal percentage of highest and lowest social classes achieve minimum basic skills mastery; (3) percentage of average and high achievers is rising while percentage of low achievers is dropping; (4) proportion of low income students at minimum mastery is rising; (5) achievement gap of low achievers with respect to grade level is decreasing; (6) gaps between racial or socioeconomic status are stable or decreasing; (7) performance equals or exceeds city-wide norms; (8) two or more independent groups perform above the 75th percentile; (9) school mean gain equals or exceeds the city-wide gain; and (10) average achievement exceeds predicted mean achievement. Each algorithm is classified according to the time frame of analysis, the level of data aggregation, the continuity of the population, and the reference norms used. Six of these algorithms are applied to data collected from a suburban elementary school 30 miles from Boston on tests of reading comprehension, mathematics, and readiness. The differing results of the different algorithms are described. (GDC)