12:30am quiet time does seem very late to me. Most campgrounds we've been to have a 10 or 11pm quiet time. The exception has been a couple campgrounds that have a "DJ Dance Party" or live band on Friday or Saturday night... sometimes the quiet time is extended until 12 midnight. We've always been informed in advance of the times, and especially if is late the management "warns" us of the late time at check in.
Sorry about your experience at the campground. We've been to many different campgrounds - some are promoted as quiet campgrounds, others as "suitable for group gatherings".... that description always warns me that there might be a party atmosphere as it is very difficult to keep large party groups quiet.
We have a private campground near us that is known as a "party" campground. If you are in the mood, it is a fun place where everyone is walking around saying hello. The issue is that the campground doesn't say this on its' website - but all the locals know it is party central.
One of our favorite campgrounds is a "rustic" state park. No amenities, basically woods camping with an outhouse available. Beautiful place, quiet hours are 10pm and strictly enforced and you are told this when you check in. We go back there often.