Access to the Lab
I can remember my days in chemistry class when everyone would have to either partner up to complete an experiment or go at it alone. At the beginning of the school year, students would quickly grab a partner and, for the most part, pick someone from their inner circle of friends. I would be a little more "tactical" when choosing partners for a couple of reasons. First, there were classmates of mine at the time that were taking more advanced classes and had more experience that made them great partners. Second, I knew that partnering up would be a much more efficient way of attacking the assignment as one could "guide" and explain the desired outcome, and the other person on the team could perform the actual experiment and execute it.