As Chevvron posted - certainly by the mid/late 60's it was quite normal to give each cadet 2 or 3 trips in a T21 to learn primary and further effects of controls and therefore being able to see how the instructor handled the controls.
The vast majority of cadets would have done the bulk of their training and go solo in the T31/Mk3.
As 3wheels posted - with the Mk3 flights we used the retrieve trolleys to whip the cadet back to the launch point (still strapped into the seat) and they would be off on their next trip in no time
For me 1st solo with 644 GS at Spitalgate in the summer of '69 (someone should write a song with that title LOL).
I later joined the staff at 613 GS Halton (1970-72) and used to chuckle at the cadets calling me 'Sir' - at that time I was a Corporal Crafty Apprentice and greatly enjoyed taking cadets up for Air Experience Flights.