Article: Children showing low arithmetic achievement received either modeling of division operations or didactic instruction, followed by a practice period. During practice, half of the children in each instructional treatment received effort attribution for success and difficulty. Both instructional treatments enhanced division persistence, accuracy, and perceived efficacy, but cognitive modeling produced greater gains in accuracy. In the context of competency development, effort attribution had no significant effect either on perceived efficacy or on arithmetic performance. Perceived efficacy was an accurate predictor of arithmetic performance across levels of task difficulty and modes of treatment. The treatment combining modeling with effort attribution produced the highest congruence between efficacy judgment and performance.