The Harkness Table is used at high dollar boarding schools, and I'm sure it works well because the students will do the reading before the class. In a regular public school all the students won't or can't do that. When there are 20 or more kids in a class it's unmanagable.

When I was in public education, we used to have so called educators come in on in-service days to pitch this sort of thing, and those of us who were teaching average or at-risk kids used to laugh at it.