While I see AoPS, Life of Fred (our family used these), and also Singapore math mentioned for math, I wonder what you all could recommend for ELA and science. Someone I know is looking for curriculum for their gifted students at a tiny private school.

English Language Arts (ELA) - Michael Clay Thompson (MCT) -
https://www.rfwp.com/pages/michael-clay-thompson/

I wondered about MCT. I know it was mentioned in the past. Thank you, indigo.