Both agencies suck.
Wait! I mean, both agencies are great.
Ah...whatever.
I like Walter's post. But in truth, unless you pay big bucks to the rare private instructor for one-on-one lessons, you are apt to get mediocre training.
But do not fret, all is not lost. IMHO, the best training comes after the class - regardless of the agency. The smartest thing you can do for you and your son is find some experienced divers to hook up with, then listen, watch and learn from them. Good post-class mentoring can teach you more than you would believe. Mentors do not have to sell you gear to exist, they are not hooked to an agency or product brand.
There are some unsafe divers out there that you don't want to be mentored by, so be selective.
BTW, good for you, taking up scuba with your son! My dad and I trained together when I was 13, and I'm absolutely positive that all that diving together through the teen-aged years kept us closer and kept our relationship strong during a difficult time.