Also, final class enrollment for the term may be significantly different from first day of class enrollment.
Perhaps on the SCPD. The point though is that even with large class sizes of 500, 600, 1,000, they can be delivered in a valuable way if the school is equipped and staffed to do so. Some, not all, can pull that off.
But back to the question as restated by @gardenstategal
When our S started at Stanford he very much felt as a small fish in a large pond. This came as a surprise to us because his academics were so strong (4.0 UGPA, 2400 SAT). He would continually speak of his friends that had so much more CS, math, and business backgrounds. However, over time (he just started junior year) he now feels like a big fish in a big pond with confidence built along several vectors. First, he now recognizes that he performs well along side all the other students. Second, he has taken advantage of research opportunities where he works alongside PhD candidates that encourage him and push him to learn more. And, finally the internships that he landed for freshman and sophomore summers have expanded his capabilities and confidence as well.