Have you tried using a work cycle with him?
Something along the lines of:
A - Attitude (5 secs)
L - Lookout (15 secs)
A - Attitude (5 secs)
P - Performance Instruments (1 sec or less)
I was taught this only recently myself but it is a great little thing to unstick a students attention from the instruments. You just have to get them scanning from the attitude to the lookout to the attitude to the performance inst etc. etc.
It's just like an IFR Instrument scan adapted for VFR use, where you concentrate on the lookout and attitude instead of the AI.
Just a thought anyhow
grade_3