The current study investigated the effects of the concrete-representational-abstract integrated sequence (CRA-I) for teaching fifth grade students receiving tier two interventions within a multi-tiered system of support (MTSS). The research questions addressed the following: the extent to which students' rational number skills changed as a result receiving CRA-I, the extent to which students receiving CRA-I decreased their fraction estimation error, the extent to which students receiving CRA-I and their teachers perceived it to be socially valid, and the extent to which students who received CRA-I intervention maintained their performance two months after instruction. Using a quasi-experimental design with randomly assigned matched pairs, researchers taught 11 students using CRA-I and compared their performance to 11 of their peers in a comparison group who waited to receive intervention. The researchers found a significant difference in performance favoring the CRA-I group. The implications of the results will be discussed.