Lew,
Finding a good instructor is like finding a good mechanic or a good barber. You may have to try a few before you find a good one. Unfortunately I am in Louisiana so I guess I don't get the job
Here are some suggestions:
Ask the instructor if they have studied either of these books:
Harvey Penick: The Little Red Book
Homer Kelly: The Golfing Machine
Ask who there influence in teaching is. Ask if they teach mechanics or feel. You want a teacher of mechanics at that level. Find out how your son learns: Visual or through oral instruction. Find a teacher who teaches how your son learns, he will make gains faster.
There are alot of great teachers out there. In my area I have a PGA Pro who owns a par three course. Great teacher, hee can teach right or left handed, short game ( he can consistantly hit pitch shots into a horse trough from forty yards of the concete cart path with a sand wedge!) His knowledge of the game is fantastic.
A start would be to look on the web for instructors in your area, ask around about there reputation.
GolfBald