In my case, instructor (also casual) had 2 students that day. There was plenty of time between our sessions to administer tests
So either the instructor was only paid for the 2 hours of flight training, or the school paid them for the 4+ hours of duty as per the award with less than 4 hours of revenue in the door.
Don't get me wrong, I waive plenty of incidentals to foster goodwill and loyalty but the school is entirely within its rights to charge for the 2 hours or so required to administer a PPL or BAK, mark it and review it with the stude.
...especially now that we have to generate a syllabus-referenced KDR too.
BTW Comrade,far more likely to call you a cnut face to face than in writing.... but the inflections and facial expressions might have conveyed better the nuanced intent.