I think kids can learn a lot trying to explain something to somebody else. The trouble is most kids have a hard enough time just being students. Arguing that they can learn more from other kids than they can from their teachers is ludicrous.
Forty minutes talking with all my students usually better serves their education than two minutes talking to each of them. Reformers, including TBL (team-based learning) boosters, rail against "sage on the stage" teachers who try to "impart knowledge," as if that's a bad thing, but the fact is I can usually lead my students better than they can lead themselves. If I can't, please show me the door.
If you disagree, please derive the Quadratic Formula and then get back to me.
Yes, I know that scientists and people in just about every other profession work in groups to solve problems. There's an underlying assumption, though, that everyone in the group is knowledgeable and that they all bring something to the table. That is not the case in school so much of the time.
Group work has its place, but certainly not as a primary pedagogical tool in K-12 education.