thanks jerry ,yes it depends what are your reasons for teaching if it is to pass theory c;lassical exams or is to help people who wish to learn tradtional music and develop their ear, if it is the latter [which is important too in classical aural exms]then learning intervals between the notes is good,
and since most people know the sound of a major scale and understand the sound of a major scales. to demonsrate it aurally is in my experience a good idea then to demonstrate modes aurally.SO PEOPLE CAN HEAR this is more important than waffling on about the crucial points of the Dorian mode are that it's a minor mode and that it differs from the natural minor (or Aeolian mode, if you prefer) by having the sharpened 6th. If i taught like that my pupils would go away baffled and confused,
far better in my experience to play a sound they recognise the major scale play it in a couple of different keys and then play the dorian or mixolydian mode with different starting points SO THEY CAN HEAR THE DIFFERENCE
AND IF ITS EXPLAINED THAT MAJORSCALES DON ALWAYS START ON THE SAME NOTE, AND THEN PLAY THE DIFFERENT SCALES so they hear them aurally , in fact they all have different starting points, SO do MODES, baffling people who learn by ear with technical terms without demonstrating the modes aurally is bad teaching.