How were your DC's experiences? How many do you have? Did you have proms yourself growing up?
DS had one in year 11. A spring ball for the whole of 6th form in year 12, the same spring ball in year 13. After A-levels he had another one.
The first and last ones were organised privately, but the school themselves organised the "spring balls", with the teachers there as well.
The year 11 one the venue strictly did not serve alcohol at all because everyone there was at most 16. The ones after had a bar for the students that were 18.
DS told me that at his 6th form balls, lots of people were tipsy and there was a fair amount of snogging (even between people who weren't couples).