This gives the town a vibrant nightlife. Some streets, such as the Rue Saint Michel, have only bars on both sides. (The locals actually call "Rue Saint Michel" "la rue de la soif", which means "Street of Thirst").
A stroll down Rue Saint Michel on a Friday or Saturday evening is a very interesting experience indeed. However, if you're really in the mood to "faire la fête", celebrate or just have fun in other words, the most exciting night on "Rue de la Soif" would be the "Jeudi Soir", Thursday nights, during the school year.
Jeudi Soir is the night when bars are most often packed to the brim with students. The sights on Thursday nights out on the town are very memorable and interesting.
Enjoy your stay in Rennes !