My son enjoys the hobby and certainly shared it in his interviews when discussing personal interests.
But, he’d taken it somewhat further than it sounds like your son has (for the moment anyway!) Yes, he had taught himself the various algos for solving and continually worked to improve his times. But, he’d also done a deep dive into cube construction and tinkered with cubes to improve their physical performance, and also competed regularly.
We’d often drive 1-3 hours (!) to get him to competitions. Though his solve times dropped to around the 10 second mark he was never truly competitive in terms of winning competitions (most larger competitions attract kids who can solve in 5-7 seconds…the official WR is 3.47 seconds and no I’m not kidding). That said, his depth of interest and perseverance is something that I think stood out in interviews. He was really into it. And that I think is something that a school may find of interest.
Not sure whether many competitions are being held these days but if so you’ll find them here:
Even if your DS and DD aren’t competitive in terms of having a chance to win, they may find it fun to be officially timed, and it may spark further interest. Good luck!