Seems a bit odd, I used to drive tractors for years before I learned to fly, and one of the first things you learned to use is the big red "PULL TO STOP" button, rather like the mixture "idle cut-off". Designed this way, as in aeroplanes, because of the human tendency to pull due to muscles contracting due adrenalin when in an emergency situation, such as about to bale the boss's prize sheepdog, or turn the boss's missus into silage additive. It's been a while, but I seem to recall the hand throttle is "pull to stop" also. Maybe Aussie tractors are different. At least your student will have plenty of experience in turning tight corners when taxiing using differential brake!
Be nice to tractor drivers, the only time they are the enemy is when you are running late and get stuck behind one on the road (rare in Aus but you English folks will know what I mean!) One of my most ignominious moments as a tractor driver in England was being cursed by the driver of a hearse for holding up his funeral procession! :o
[ 14 December 2001: Message edited by: Charlie Foxtrot India ]