The summer camp I attended when I was 8, 9 and 10 participated in a "camp train" that ran from GCT up the Housatonic River Line to the Berkshires (presumably to Pittsfield, though we got off in Great Barrington.) This was in the early 1960s and the New Haven ran the train. I seem to recall the cars were pretty beat up, but it was a fun ride, anyway, kind of like a New Yorky version of the Hogwarts Express. They passed out cartons of milk at Danbury, that was all the food we got. The other cool thing about this was that I got to ride the PRR from Philly to New York and spend a night in Manhattan in order to catch this train.
When I was 14, in 1968, our Scout trip to Philmont involved riding the CB&Q Denver Zephyr, and we not only had a car to ourselves, we also had our own dining car that served food that I'm sure wasn't as good as the stuff served to the regular passengers. It was still a fun ride. They let us go visit the rest of the train, ride in the dome car, and I bought a pizza in the "Chuckwagon" car to supplement the inadequate fare we got in the diner.
More recently, on Amtrak, I saw what looked like a school group on a class trip get on the Cardinal at Prince, WV, and get off at White Sulfur Springs. I was in a sleeper, and I don't know whether they had a car to themselves. Amtrak also runs charter trains. In fact in 2018, they ran a charter train taking Congressional Republicans to the Greenbrier at While Sulfur Springs that hit a garbage truck at a grade crossing in Crozet, VA..
https://www.nbcnews.com/news/us-news/train-carrying-gop-lawmakers-retreat-hits-trash-truck-n843311