QUOTE(nickjones8 @ Nov 26 2008, 10:20 PM)

QUOTE(BerkshireMum @ Nov 26 2008, 10:17 PM)

Have you tried his instrument yourself, or let him try yours? It could be a problem with the instrument.
That's the obvious suggestion. It may well be a small leak higher up the instrument. Can he subtone the notes - if so, a leak is less likely, and we're probably looking at breath support (a different matter, as you know, from lack or air!)
And what is a not particularly hard reed?
I'd try the horn yourself.
nick
This would be my first thought too. The more experienced you get the more capable you become at "blowing through" leaks, so even if you can play it he may still struggle. I'd take it to be looked at by a tech, it may well be that a service is due.
In terms of specific exercises it's all the usuals really, long notes (throughout the range of the instrument, not just at the bottom), overtones, scales over the range of the instrument. He could try the exercise of fingering F, E, D with the octave key and sounding the lower octave note.