When I was a driving instructor, the most problematic ones were the adults who decided to go get their license but had to do a set amount of instruction beforehand. The adults who are the absolute worst are the ones from India, Nigeria, and China. The language barrier was the least of my concerns and having a right-hand side brake pedal was sometimes not enough ease my nerves.
With teenagers who supposedly have all these anxiety issues. It didn't take long to understand where they're getting their issues from. It was sometimes a mix of both parents. It was mostly the overbearing helicopter mother. Doing some talking with the kid during the lesson usually eased them up. Once they eased up, it opened them to listening to what I was trying to convey. Once it clicked in their mind, the lesson(s) became so much better.
There were times I wanted to tell certain students they aren't cut out for driving. Management told me I can't say that. I asked, "why?" Their answer had something to do with making money. Well, some people are better off relying on public transportation, rideshare, or friends and family! Most defensive driving companies' main priority is to make money. They genuinely don't care about what they're putting out there. The one I worked for is like a license mill so they can get a cut from State Farm Insurance for each student whose parents sign up. I left due to the obvious it was more like a license mill and they weren't interested in actually teaching people valuable REAL WORLD driving skills. With the immigrants who were having an extreme difficulty assimilating to the road customs in America, the company is only interested in pushing lessons on them in order to make more money.
Trucking schools have been facing immense pressure to pass through incompetent drivers who fit a certain demographic. I'd hate to be an idealistic instructor at any of these trucking schools. It has to be maddening. It's all fun and games until one of those fools kills somebody or some people and the school where they did their CDL "schooling" gets looked at. Schools like those get shut down all the time.