More of a university type deep dive approach, this is exactly what I had in mind Leapfrog.
What I had in mind in totality was this...
Literacy (mathematical, English, financial, computing, economics, politics, home studies etc - a basic understanding of a huge range of topics they'd need for life.) Progression is according to LOs met, so class composition would change all the time.
Broad interest - topics introduced every week with choices on what to go to and recordings to catch up on a HUGE range of interdisciplinary subjects (various periods of history, architecture, farming, fashion design, everything you can possibly think of). This could be mixed age and ability.
Special interest - topic and project work at an advanced level, focused on both input AND output (composition, writing papers etc) and interaction with subject area experts.
Extracurricular - sports, music, chess, huge range of clubs with local schools not for the gifted
Psychological and emotional support - teaching social skills and resilience, offering therapy if necessary.
Realistically because of ratio of staff to students and support needed, I think it would have to be a very small private school. Can have full scholarships for 10% of the school, plus support packages, for those from lower socioeconomic backgrounds.
entrance would be a huge mixture of tests and interviews that would weed out the children from pushy parents and also account for socioeconomic differences.
Not that I've thought about this much 