This article presents findings from a comparative case study examining the implementation of the mathematics strand of the Key Stage 3 Strategy in two contrasting schools--one using setting and whole-class teaching, the other incorporating mixed-ability grouping and individualised learning. A number of "outcomes" of implementation are considered, including teachers' and students' experiences, changes in pedagogic practice and students' attainment. Whilst both schools achieved highly in relation to similar schools, higher attainment gains between Key Stage 2 and Key Stage 3 in the school using setting/whole-class teaching were associated with increasing student disaffection and dependence on teachers. In contrast, the attainment gains at the school using individualised learning were associated with increasing enthusiasm and independence. The mixed picture of outcomes and their complex interconnections suggest that evaluations of implementation resting on attainment-based outcomes are problematic in terms of longer-term aims of increasing the proportions of students choosing to study mathematics and developing the skills of independent learning. (Contains 2 tables and 1 note.)