Enigmaviation,
I can assure you that all cadets passing through Benson for AEF flying are required to demonstrate not just the knowlege of how to use the parachute but also how to safely remove it when being dragged in the wind.
After a mid air the crew are at the very least going to be very confused and disorientated. If the cockpit is damaged then possibly unconcious. It the wings or tail are damaged then the aircraft is probably going to be rotating violently. I would imagine escape from any aircraft after a mid air would be very difficult.
What is the accident involving a cadet in 1995 ?
I have carried out jettison/abandonment drills in both Bulldog and Chippy as far back as 1980 and the drills always worked for me.