I think that when you look at a long time frame then it is hard to argue against this idea. Would today's learners be just as well served in a cave with some blank wall space and a burnt stick?

The more interesting part of the question for me is "how come we still have so many classrooms looking like what they did when I went to school - surely that's evidence in itself that what we're doing is working - or is it?" I think that society has found 30 students sitting at desks and receiving their education from one teacher at a time very convenient, and it has been a solution that has been seen to "work". But the reason it has worked and found a reasonably high level of acceptance is because schools have such a broad range of services, both formal and informal, that they provide to such a diverse group of clients. The status quo has been seen as an acceptable compromise I believe.