Stanford is known for its great academics. You can take any class you like, and if a desired class isn't offered, you can work with a department and an adviser to start a new class. For upperclassmen, it is very rare to have a class that has more than 30 people. Most classes are very small, and you have the opportunity to build relationships with award-winning professors. Stanford is all about collective learning; it is very common for students to be actively involved in study groups for their classes.
Professors are highly accessible and truly make an effort to get to know undergraduates. Some students may feel that their introductory classes are too large, but the overwhelming sentiment is that the education you get here truly is first rate.