Driving instruction has one purpose, to obtain your CDL. I did mine in 7 days. 3 days later I was OTR with a finishing instructor from my employer.
His was through a college and was about 6 weeks.
Several years ago, I had a Class B with Passenger endorsement. Drove coach buses as a volunteer.
Many years before that, I had a chauffer license as a church youth group leader to drive the church van. When CDL came on, I read the book, took the test then did my road test in a fifteen passenger van. Suddenly, I’m licensed to drive a 49 passenger bus.