Handling large-sized classes and maintaining students' involvement are two of the major challenges in Personal Software Process (PSP) education in universities. In order to tackle these two challenges, we adapted and incorporated some typical practices of Pair Programming (PP) into the PSP class at summer school in Software Institute of Nanjing University in 2010, and received positive results, such as higher students' involvement and conformity of process discipline, as well as (half) workload reduction in evaluating assignments. However, the experiment did not confirm the improved performance of the paired students as expected. Based on the experience and feedbacks, we improved this approach in our PSP course in 2011. Accordingly, by analyzing the previous experiment results, we redesigned the experiment with a number of improvements, such as lab environment, evaluation methods and student selection, to further investigate the effects of this approach in PSP education, in particular students' performance. We also introduced several new metrics to enable the comparison analysis of the data collected from both paired students and solo students. The new experiment confirms the value of pairing practices in PSP education. The results show that in PSP class, compared to solo students, paired students can achieve better performance in terms of program quality and exam scores.