Farm families have been doing such for many decades with relative safety. Of course, wise farm fathers insure the child is well trained AND THEN STILL WATCHES ALERTLY IN HAZARDOUS SITUATIONS.
Sorry I'll still don't believe a 4th or 5th grader has any business under any circumstances driving a car or truck. My great uncle farmed over 2500 acres and my 2nd cousin was alwayy complaining that Uncle John wouldn't let him operate the tractor or the combine till he was 14. Although from the age of 12 he did get to pilot the riding lawnmower.