I once took a job as an instructor in one of those outfits in florida...they taught lots of foreign students.
I went there and poked around a bit...saw a trainer with its engine running and no one in the plane.
I asked about it...seems some of the students were happy to build time by letting the engine run, while parked , and going in to get coffee.
AS the chief pilot's name reminded me of a famous clown, I elected to leave the establishment and would not ever do business with them.
there is nutty stuff going on out there...so be careful