Our school always has an adults only disco
BYO drinks, usually with a theme, this year was Casino Royale I think
We also had a winter ball this year as a major fundraiser. Very big deal, 3 course meal with entertainment and dancing.
Another year we had a "girls night out" - 3 course meal, function room with all the local party plan people in attendance (scrapbooking, candles, chocolates, lingerie etc). Raffles, hairdressing makeover on the night. Really great night.
Trivia night is every couple of years.