I went to both my Year 12 and Year 13 proms (equivalent of junior and senior proms). Didn't have a date for either but then neither did most of the people in my year (school came down pretty heavily on showing affection in-school, which tended to reduce the number of "official" couples). There was definite pressure to attend at least one prom but nobody was expected to attend both and several people skipped the Year 13 prom with absolutely no social consequences.
Didn't see any point in getting myself a prom outfit on either occasion; some formal clothes that were slightly fancy but also perfectly suitable for university interviews, open days and other formal events proved a good investment, serving for both proms (with slightly different accessories) and about two years of other activities.
Food was served before the music was turned on in both cases and I think that helped a lot. It's difficult to properly enjoy a three-course meal if you have Britney Spears blaring at 120dB in your eardrum (and yes, I have been to places where that unfortunate mistake was made).
There was loud music but only at one end of the places where the proms were held. So there was a "loud music" dancefloor, a "quiet music" dancefloor and an "escape zone". This meant I had somewhere to go when I felt like dancing (the "quiet music" floor - even with earplugs the "loud music" dancefloor was impossible). The Year 13 prom music was provided by a brass band rather than the usual disco studio set-up, so it was fun to listen to it even when I couldn't tell what pop song they were covering.
In Year 12, the "escape zone" included an event photographer (I've still got the photo of me with my two best friends from school on my bedroom wall) and a piano. A whole bunch of us spent part of the evening entertaining each other with various songs. In Year 13, there was a huge garden which everyone explored at some point. The fact that my friends and I explored it for about a third of the time we were there was considered absolutely fine, except for the one that got too drunk and ended up falling asleep in a plant pot (luckily I'd left by the time that happened).
In short, the proms were great but that was because they'd been adapted to appeal to more than just the people who wanted to dance the night away. I get the impression that a lot of proms are not.
However, I will say that I skipped the university prom on the grounds of value for money. I didn't see the point of spending £40 on a night out that, due to transport issues, would have lasted the grand total of 2 hours...
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