The throat extension Fungo showed will prevent an injury to the front of the neck but if he is turning his head, that needs to be corrected. Shots to the neck are a serious matter.
Saw a catcher from Southern Miss get hit flush in the throat (foul tip) in the days before masks had built on extensions or flaps. Scariest thing I ever saw on a baseball field; won't go into details but I never want to see/hear that again on a field. He ended up spending two nights at the hospital in Opelika before getting released to head back home.
Alot of good advice has been given. It's something to take seriously.Ever done the "ball to the facemask" drill so he gets back to to trusting his equipment totally? Pretty sure you have if he has caught for length of time. Can't control foul tips but he can control staying square and not turning with practice (it isn't natural to just stare at a pitch as it hits your facemask without wanting to turn).
Fungo mentioned "jabbing" and he's right...catchers don't jab, they recieve the pitch; sometimes catchers jab in an effort to "Beat the ball to the spot" that they hear from coaches. It starts with how they track the ball...jabbers tend to track with the glove which is actually slower and jerky. Work with your son in tracking with his eyes and taking the glove from a relaxed position up to the point where he thinks the ball will be ( he'll be smoother and find it easier to make adjustments).
The very first thing I always told catchers Rule#1 was "Protect yourselves...trust your equipment...always".
09 Grad...probably been catching awhile and knows everything I've mentioned and the two shots were probably flukes. Problem is that one fluke can mess him up badly. Good luck to your son getting a handle on this...I'm sure he was just as scared as you were.
By the way, if the shock of foul tips to the facemask are making him gun shy for some reason, you might check out the new Wilson Shock FX helmet with the shock absorbers. Don't know if they work real well or not but the concept sure makes sense.