Having flown at 3 different schools while restricted, I have asked each of my supervising instructors about the level of supervision required.
One insisted he had to be present at the airfield, another was happy for me to fly when he wasn't there but not to send anyone solo, and the third was ok with me doing whatever I wanted while he was on holiday for a week.
Since the legislation on this point is very unclear, and the CAA don't really give a proper answer, who can give a definitive answer on what supervision really consists of?
It seems to be designed for a busy school with plenty of students, since you need to obtain 25 solo sign offs. Would it not be better to have to evidence that you have taught every lesson in the syllabus at least once, rather than just making up the time with Ex 3?