I got a class ring in high school. I only wore it while in high school. It was bulky and I do not like anything bulky on my hands. Looking back, I believe it was just a right of passage kind of thing.
I also got a college ring when I graduated college. That ring, I truly treasure because I had to work so hard to put myself through college. It does not look like a traditional class ring. It looks like a nice emerald ring. You have to look at it very closely to see that it is inscribed with my school name, degree, and year. My full name is inscribed inside it (very tiny).
I can relate to your shock over your son not wanting a class ring. Maybe you should discuss it with him. Ask him to help you understand why he doesn't want a class ring. He may have some very valid reasons as to why he doesn't want a ring. Either way, doing so may help you come to understand his decision and his logic behind it.