Perhaps you misunderstand me, Hugh. People are complaining that it takes
up so much time to do the copious derivations, that they don't have time to
tech in discussion (ie Socratic) mode. I say that by far most required
derivations are simple enough that they should not take very much time to
show on the board. So do them and move on. Students are not dumb -- only
lazy. Few of them are even as difficult as SR.