At my church, we have several Sunday School classes for the children, and they move up through them like in regular school. Each September begins a new Sunday School year - almost like the schools.
The adult classes also have several choices. I'm in the college/career class. There is also young adults and several classes for married couples to choose from. We even have some classes that are separated between the men and women, if people prefer that.
As far as what is taught, we buy books every quarter, and that's what most classes use. Nearly every Sunday School class in church is learning about similar lessons. I know that the Jr. High, High School, and College books are written by the same person and are very similar in content. The youngest children, I figure, learn mostly Bible stories, rather than applications gained from those stories. The older people learn the same story, but also go further in depth with the applications of the story.
We have some discussion type classes, but most of those are on Wednesday night. Since I teach AWANA, however, I don't get to have a class I go to on Wednesdays. That's not saying that teaching AWANA isn't a learning experience, because it most certainly is, but it's not really Bible study and discussion.
I think my church is blessed with several ministries, though. There are many Bible study groups that meet throughout the week, and Sunday School is a good way to learn the Bible's content so that the lessons can be applied to life. Even with our more lecture-style lessons, we still manage to discuss things fairly often. All-in-all, I like our system for Bible study and Sunday School.