No one or two or five gyms/kwoons/dojos/whatever prove or disprove the validity of an entire art. How do you test the validity of what a MMA gym teaches? You ask who the fighters are and what their fight records are. Oh, you don't produce fighters? Hmmm, that should raise red flags.
How do you do it for a karate studio? How do you do it for Joe Bob's Tactical Fisticuffs that just opened up with all the new evolved fighting method?
That is why to me you should NOT only look for a Martial art that fits you but an instructor that is appropriate. Below is a rough approximation of how I did things and it took me almost a year to find a guy that wasnt a 35-45 minute drive away that taught Inosanto Kali and as a combative to boot. If my Guro/Sifu ever retires I will like be forced to drive that far because it's only other place that teaches it as a combative in the area. Critiques of the following process are appreciated.
Before you even try the school out...
1. Look for a Martial art that was designed for combat/real fighting vs point sparing.
2. Talk to the instructor. Don't ask him what he teaches you should know that before calling/emailing. Rather be honest and say something like I did. I made it clear to numerous instructors that I was a LEO looking for martial arts training that first and foremost had practical street applications. I lucked out maybe in that I had 3 instructors that said yes (the two Kali and one KM) but a number that were honest the other way as well. Some may have hedged and said "well it can be used for self defense" but they were honest and said that for my application, not so much.
3. Listen to how they describe their style of teaching. Do they say "street encounters" or "combatives" vs "self defense", "competition" and "discipline". If they say things similar to the first 2 ask them if they teach outside the school. If they say they do seminars and blocks of instruction for local, state or federal LE (which can be verified rather easily) you are probably on the right track. Don't be afraid to ask if they have experience in real defense situations.
I say this one because if they teach stuff to LEOs it will get around if its crap on the street and the contracts will dry up.
Try them out, most schools let you at least for a class or two. If they do...
1. Do they have tween or younger black belts? That imo is a red flag.
2. Do they spar when you are there? If not ask their rules. If their sparring is point based and stopped, to me this is a red flag. If however the sparring is all out for seniors, (controlled for juniors), and then after time, safety stop, tko or submission etc, an evaluation is done this is a good sign because fights don't stop for points. Example when we spar with Knives in Kali we put chalk on the knives. Our uniforms are black. After a sparring session the Guro/Sifu evaluates who got cut more, where and how severely based on the chalk marks but during the fight it is all out. If you aren't breathing heavy you did something wrong. Yes we wear gloves, forearm guards eye protection and helmets (if the head has been declared a viable target.)
3. What techniques are taught. Just about every Martial art has "cheap shots." Are they taught or simply talked about?
There are other things as well, some you may not discover for weeks or months after you start, but these I think are a good starting point to determine if you should sign that contract.