Sixty first-grade children from two different socioeconomic levels were presented a concept-acquisition problem after either 0, 6, or 12 trials of random reinforcement. The overall performance of the high-socioeconomiclevel children was superior to the low-socioeconomic-level children, but the results also indicated a significant interaction between socioeconomic level and number of random reinforcements. With an increase in the number of random reinforcements, the behavior of the high-socioecenomic-level children deteriorated to the same level as the low-socioeconomic-level children. The experimental manipulation of prior reinforcements produced low-socioeconomic-level behavior in high-socioeconomic-level subjects. The data are interpreted as further evidence that the inconsistent reinforcement histories of low-socioeconomic-level children contribute to their typical ineffectual performance.