2 things i can think of.

put the plane on the ground in front of the student with the transmitter and plane turned on (engine NOT running) now talk the student through a flight from take off to landing "right aileron, a bit more, pull in some elevator to keep it level" etc do the whole circuit from take off to landing with you and the student watching the control surfaces, see if that helps.

also get them to down load FMS and tell them to practice at home on the PC.