<p>To keep options wide, recognize that the vast majority of colleges will challenge your son: it has more ot do with the chosen major, what your son will take for courses, what he will take on as opportunities, than anything to do with which 'rank' it is. Physics at number 10 is the same as Physics at number 20. </p>
<p>Also to keep options open, realize that a small school does not necessarily mean you can banter with the teacher and use your personality in class oreven know faculty well; likewise, a large school doesn't mean that won't happen. Depends very much on the structure, size, policies and cultures of a given program and major.</p>
<p>Just to give an example (and there are many): I teach at a school with 40,000. Some of my classes as small as 15, never more than 50 (only our freshman classes have about 100 students, and that is not an uncommon at that level for even for top 10 national universities). I know every single one of the students in our major, as do my colleagues. It depends on so many factors. My real point being just be sure to closely investigate when you get closer to the decision point, so you don't have to rely on assumptions.</p>