Hmm, I think it does depend on whether you mean amazing for them or totally amazing for anyone.
So if you're bowled over that they've managed to get their grade 1 in piano getting 101 (pass mark 100), then possibly mention it to the music teacher who supported them having a go when they were clearly non-musical (or that told them they'd never do anything musical in their first week), but not inform the head.
If they've been invited to tour with a world famous orchestra over the summer. Then yes, they'd like to know.
Obviously that's quite a gap
So I think you slightly play it by ear depending on otherer stuff that goes in newsletters or how many other pupils there are type of thing.
So roughly at secondary, I would say:
Don't tell: personal bests, club teams, exam marks, general awards, performing in local am dram.
Possibly tell: County teams, big (at least intercounty) sporting results (probably only gold/silver), grade 8 music, (particularly lower years), the main part in auditioned am dram.
Do tell: England squad, national results, national youth orchestra, professional part (they'll need a licence anyway)
That's roughly what I see in the newsletter. Very big comp though, I suspect a smaller school may have more interest in the possibly tell category because they can aford the space.
I've not felt the need to tell primary or secondary of such stuff at all unless it's effected the school, but maybe I'm wrong, although dd1 would certainly sink through the floor if I did.