know a lot or assumptions but 5 instructors with 5 students. why not tandem urgently and pull the cord immediately? could it have been worse?
May not have been high enough to try or happened too quickly to even get the door open. Article says the plane veered off to the right and was seen falling verticially.
Very sad and such a shock for the friends and family watching on the ground. 
It crashed immediately after take-off, just 300m from the runway, re French news reports, so it’s likely that it happened too quickly for anyone to even think about doing anything.
It’s heartbreaking…