The back-pressure based scheduling policy originally proposed by Tassiulas et al. in [1] has shown the potential of solving many fairness and network utilization related problems of wireless multi-hop networks. Recently, the scheduling policy has been adapted in random medium access protocols such as CSMA/CA using prioritization of MAC layer transmissions. Here, MAC priorities are used to provide differentiated services to nodes depending on their queue backlogs. Even though these schemes work well in experiments to emulate back-pressure scheduling, they perform poorly with realistic Internet-type traffic where there is a large variation in packet sizes. In this paper, we propose packet aggregation based back-pressure scheduling which aggressively increases the rates at which back-logged queues are served. Different from other aggregation schemes, the presented scheme utilizes the back-pressure principles for determining when and how much aggregation is performed. We show that this results into increased service rates of back-logged queues which in turn results into high network throughput and utilization. We verify our scheme using simulations and testbed experiments, and show that it achieves significant performance improvements as compared to the original scheme.