Check-in/checkout (CICO) is a behavioral intervention that is used to provide systematic feedback about a student's behavior at the beginning and end of each school day. The purpose of the present study was to evaluate the effectiveness of CICO on decreasing problem behaviors and the collateral effects on mathematics performance for 4 at-risk elementary school students. A multiple-baseline across-participants design using dyads was used to analyze problem behavior collected through direct classroom observations. As ancillary measures, office discipline referrals per week as well as mathematic performance (i.e., digits correct per minute [DCPM]) were collected for each student. Treatment integrity and acceptability and social validity were also measured. Results indicate a decrease in problem behaviors as well as an increase in DCPM for each participant. (Contains 2 tables and 3 figures.)