Students need to learn and practice computational thinking and skills throughout PreK-12 to be better prepared for entering college and future careers. We designed a math-infused computer science course for third to fifth graders to learn programming. This study aims to investigate the impact of the course on students' knowledge acquisition of mathematical and computational concepts, motivation, and perceptions of the computing activities. Fifty-one students at a Boys and Girls Club participated in the study. Data collection procedures include pre- and post-tests, pre- and post-surveys, in-class observations, and one-on-one interviews. Results indicate that students have improved significantly on mathematical and computational concepts. They also tended to believe computer programming is fun, comprehensible, enjoyable, and were able to perceive the value of learning it. Implications and recommendations for future research are also discussed.