I attended a large state flagship university, (Indiana) but I majored in Comparative Literature and ALL of my classes, save two - , a math class for non-majors and an introductory art history course - were less than 25 students, and in a regular classroom, and discussion-based. All of the classes in my major were 15 students or less.
(The math class was in a huge lecture hall and had more than 200 students. The art history course was in a smaller lecture hall and had over 50.)
I also transferred in from a smaller LAC (where ALL of my classes, even science classes and labs, were 20 students or less), so it’s possible that some of the intro gen ed courses at the huge state U were in big lecture halls.
But my point is, if you’re a humanities major, or in a major that’s not very popular, you may end up in very small classes no matter where you go, especially as you get into upper-level classes.
eta: Just saw that OP’s son wants to major in CS. That is a very popular major right now, and bigger schools will most likely have much bigger class sizes, and less individual attention. An LAC will have smaller class sizes (double check that they offer CS, some LACs only offer the traditional Bio/Chem/Physics…)
I started out as a Biology major at an LAC and NONE of my intro classes were in lecture halls, they were all in regular class rooms with no more than 20 students. Labs were small, too.
The other nice thing about LACs is that all classes are taught by professors (although a couple of my TAs at Indiana were better teachers than a few of my professors, honestly; having a TA is not always a bad thing).