tes that the practice benefits only the gifted... Regardless of the methods used to place students, the effects of ability grouping are uniform; furthermore, placement in low ability tracks is uniformly correlated with socio-economic status and race, I.Q. or achievement test scores notwithstanding" (p.6). Raze (1984) came to the conclusion that ability grouping "can be devastating for those in the low ability group" (p. 7).
One of Slavin's (1986) studies concluded that "overall, evidence does not support assignment of students to self-contained class according to ability (median ES = .00), but grouping plans involving cross-grade assignment for selected subjects can increase student achievement" (p.1). As we shall see, moreover, the Joplin Plan has been found to be instructionally effective (median ES = + .34).
In view of these contradictory findings, whom are we to believe?
Slavin (1986) remarks that "one importan
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