I would be loathe to denigrate a former employer or a flight school. The likely result of either course of action is likely to come back to haunt you. Shut up and walk away. Don't pan, don't give a recommendation, don't diss, but above all unless you have conclusive evidence of wrongdoing zip your lip. Entitled to that opinion, yes, Broadcast it, with expectations of other opinions yes. Bear in mind that employers frequently use the phrase "No recommendation" to rid themselves of liability for dissing former employees. "No recommendation" says much. and you will not like the results of that if you are seeking employment. I've just watched a professional politician destroy his career because he didn't have sense enough to shut his trap.
Sgt Schultz is out. Dumbkoffs rule.
Disclaimer: The above was not intended to be political. It was an observation on how things work in reality. No unicorns or rainbows, just truth as I see it.