I wonder how Peggy could tell the pregnant high schooler wasn't married? Or did she just assume it?
My mother was pregnant with me when she graduated from high school, but she was married to my dad, who was drafted for Korea. Despite the fact that she was 1) married, and 2) had the highest GPA in the graduating class, they not only didn't let her be valedictorian, she couldn't come on stage to pick up her diploma.
Peggy might think that was a better way of doing things, but I don't.
I would imagine your mother knew before she married your dad that she would not be allowed to participate in the ceremonies and accepted it. Now, the ACLU and a host of other liberal activities would try to convince her the system was trampling on her rights.