The third records all sound mixed from the studio mikes and playback deck. This arrangement can produce far more professional results and occupies more students. On the down side, its complexity tends to overpower the emphasis on writing and forces you to spend a great deal of time explaining what dials to turn and what buttons to push when. Some fortunate schools have radio studios or television studios with audio control booths and student personnel to run them. You can record sound alone in a TV studio.
Audio recording can keep the large studio busy, helping to justify the capital outlay.
I've found the most convenient arrangement is the most effective. If special arrangements, travel plans, or intensive instruction are required to get you and your students from where you write to where you record, the teaching strategy is likely to be more cumbersome. You might like to try making the recording process even more convenient. Furnish a classroom with several multiple listening station recording machines and allow several groups to record at once. Room dividers can soften the noise between stations and allow some privacy for the groups or individuals recording.