Well, at his request, I bough him a 'flexable' metronome that "talks" and stresses beat counts and all sorts of interesting stuff, in an effort to help with counting.
One thing that I saw last year is that once he got some things 'down', if one changed tempo he was stumped. So I said lets back up and start with scales etc and work on counting and tempo changes. It was ugly. He is also ADD, and although he is entering highschool, it seems that he forgets note/slide position and even sounds. Poor little feller, has the curse of short arms to boot. I wish he had chosen the stick, I have a LeBlanc and Noblet Bb sophrano, but his mom played the trombone.
His teachers and tutors rant about his sound, I don't know much about brass as I played almost the entire line of clarinets in my mispent youth - from that nasty little Eb toothpick to my wonderful contrabass; it was awful, I went from the contrabass that I had been playing for three years during high school to that toothpick in college at my director's insistance. Yuck, sitting and playing right up there where there is no air, and not to mention hardly any white on the sheet of music, with the piccolos. Severe culture shock, that was, not to mention what it was doing with my embrasure. That is when I decided it would be safer on a nice quite submarine playing with nuclear reactors. ;^)