Frankly, most KOA's aren't "fancy" enough for my little bus
I "google earth" to viewany KOA I'm considering and then go from there. Usually I e-mail ahead (regardless of park ownership) and simply ask if I will be welcome in my conversion. I don't use the phrase school bus and I include a picture of my bus in the e-mail. I've never been turned down, not even at the $115/night right on the beach above Santa Barbara, Ca our s%%t doesn't stink "resort". Also, I always offer to pay in advance with a credit card. Cash talks, BS walks or in this case ends up parked behind some gas station next to the railroad track.
By the way, the BCI March gathering is one of the best run get togethers I've been to and skoolies are definitely welcome.
I think R/V park owners are mostly worried about having trashy people leave behind their ancient sagging sticks and staples (after the cops arrest them) or folks who think burning a bus tire in the campfire ring to ward off mosquitoes is OK than they are about well done skoolie conversions or the ten year rule.