Students' flexibility in solving two-digit addition and subtraction problems: Instruction effects.

This study examined the effects of conceptually based instruction on the development of students' procedural flexibility. Students from 10 2nd-grade classes (206 students) in 9 primary schools in the Netherlands participated in 1 of 2 different instruction programs: the Realistic Program Design (RPD) or the Gradual Program Design (GPD). The RPD teaches conceptual understanding along with procedural skills. The GPD emphasizes the acquisition of standard procedures. Students' use of and preference for procedures were assessed as well as their ability to solve problems in 2 different ways. The RPD led to a higher level of flexibility than did the GPD on all 3 measures, suggesting that the RPD was better in teaching the students conceptual knowledge. In both programs, conceptual understanding seemed to precede procedural skill. However, skill and understanding were closer related in the RPD than in the GPD group.