The study focused on the impact of flexible grouping on student learning during a period of time in a high-needs school. The study tracked nontransient, below-goal elementary students on multiple literacy assessments during a 5-year flexible grouping implementation. Results showed that the percentage of students attaining mastery increased in 16 of 19 over-time comparisons. Increases in the percentage of students At Mastery ranged from 10% to 57%. The percentage of teachers using flexible grouping on a weekly basis increased from 25% to 95% during the same 5-year period. Teachers attributed the impact of flexible grouping to (a) focused instruction related to particular learning needs, (b) the ability to keep student attention focused on the instructional task, and (c) increased student confidence. The results support the use of flexible grouping to improve student learning for below-goal students without the potentially negative effects of ability grouping.