Our public school PTA last year raised $120,000, 2/3 through an auction, etc. We have a lot of highly educated stay-at-home moms who sit around and volunteer a lot at the school. I think volunteering in school does help, partly since your child sees you there and understands that school is important.
I finally this year stopped volunteering in the class since I work full-time and can't do it, but hubby still does. It's definitely a lot of fun, and it gives you a birds-eye view of what is going on in the classroom.