Implementation at school A. Teacher A was an experienced physics teacher who preferred to adapt the approach to his own established set of homework problems. He reported implementing the conceptual framework primarily for more advanced problems, which represented between one-third and one-fourth of students' homework (problems with multiple steps, multiple principles, or more advanced mathematical procedures). Students were not graded on homework, however, at least one problem on each exam required students to use the approach. He was observed to model the strategy-writing aspects for students when doing example problems on the board during class (principle-justification-plan), but only used the two-column solution in an informal way.