I was 8 when this movie came out in 71, so those kids were basically my age. We were little hellions back then.
The sun shone, having no alternative, on the nothing new. Samuel Beckett

I don't think the trucker had any gripe with the kids on the bus. He had targeted Mann. He did want to kill Mann, eventually. But first he wanted to terrify and torment him like a true psycho he was.

What happened to the kids? Did the bus restart? Did the trucker push the bus over a cliff?
If the trucker wanted to kill Mann, why didn't he just smash into him at the railroad crossing?

I think the horrible kids add to the horror and suspense of the situation. Same with the bus driver not believing him when David implies that the trucker is a maniac. David is all alone in this.

Those kids will probably beat up today's ipad generation sissy kids.

I didn't mind those kids just being a little bit naughty. It's the hyperactive kids and the know-it-all kids of more recent movies that I can't stand.

Awww come on, they weren't that bad. They were a bit rambunctious, but they must have been bored stranded out there in the middle of nowhere. We have no idea how long they've been there before David arrives.
R.I.P. Rick Ducommun and Tony Longo

I first saw this movie when I was a kid in the 70s and even as a kid myself, I found those little brats repulsive. I would have never been that rude to an adult.
"Don't tell me your little problems son, all I'm interested in is results."