What was the Queen Charlotte’s Ball like after 1958? What about the last 76’ Ball?

Hi! I’m a writer and I’m toying with a new story idea set at a British boarding school that could potentially include a debutant as a main character - all set in the 70s.

I’ve been researching debutant balls in the UK during the 70s and I’ve learned the most prestigious one - Queen Charlotte’s - had its final run in 1976. I’m tempted to include that final deb season into the story.

Could any of you tell me a bit more about the last years of Queen Charlotte’s ball? More data about any '70s UK Balls is also appreciated.

Thank you!