The purpose of this study was to examine the utility of a brief assessment for the selection of an effective instruction to increase fluency performance on computation math problems. Participants were four general education third-grade students who performed below the median score on a classwide administered multiple math skills probe. Students first participated in a brief assessment within a mini-withdrawal design to compare the relative effects of a contingent reward (CR) condition to a baseline condition on math fluency performance using a multiple skills probe. All four students increased performance when given an opportunity to earn an incentive for meeting a performance goal. Increased performance indicated a performance deficit to explain low math performance and that the students would positively respond to a contingent reward intervention on single math skills. To validate this hypothesis, the effects of baseline, CR, and instruction plus CR on fluency performance over time was assessed using a multiple baseline design across three single target skills for each student. Of the 12 skills assessed, results from the extended analysis demonstrated that the CR was effective on one skill, instruction plus CR was effective on five skills, and performance improved during baseline on six skills. Post results showed improved performance on the multiple probe for all students but performance was retained over 2 to 4 weeks on 5 of the 12 skills mastered during the study. Discussion focuses on considerations of the utility of a brief assessment approach in the application decision making and for future research