Arithmetic achievement and instructional grouping

In recent years, interest has increased in various ability grouping procedures. One widely discussed grouping method has been the “Joplin Plan,” developed in the Joplin, Missouri, elementary schools and originally used to group children for reading instruction by their ability level, disregarding their assigned grade level (Floyd, 1954). The plan apparently has been popular for reading instruction and has been extended to other curricular areas including arithmetic. One modification of the Joplin Plan in some schools is that children are grouped by ability within, but not across, grade levels.