Despite the name, quarters are generally 10-week trimesters that run from mid- or late September till mid-June. There’s a two or three day break at Thanksgiving, and a two week break for the winter holidays, with a new quarter starting immediately after New Year’s. A weeklong break separates winter and spring quarters.
On the plus side, any class a student finds tedious will be over very quickly. On the down side, mono or even a bad case of strep or flu - anything that causes a student to miss more than a few days of school - can derail an entire quarter’s worth of work. Also, freshmen on the quarter system often find themselves the last of their class to leave for school, and that can be lonely. Some high school principals report finding new grads sitting in their offices in September, just wanting to hang out a little. Quarter system students are also the last ones home for summer, so they may have more difficulty finding summer jobs. On the other hand, they’ll be greeted with delirious joy by all the semester kids who’ve been home and lonely for weeks.