Someone upthread suggested you Google "super curricular" - it's actually "supra-curricular", and is definitely worth Googling.
D of E is not important. Neither of my DC did it (both at Oxford), and I wouldn't particularly recommend it to anyone. I wouldn't not recommend it, either - I just think there are more useful things you can do if you're thinking of jobs/university courses.
However... Year 7 and 8? I wouldn't be thinking about either thing at all, tbh. I'd be encouraging them to have a wide range of interests and friends, to do their best, and not to worry about what comes afterwards.
That said, I do think that parental engagement is important. Not in a 'providing expensive activities' way, but in the way of taking them to places, talking to them, providing reading matter and conversation, discussing things with them, etc, etc, etc. It's hard (not impossible, but hard) for a bright child with completely unengaged parents to do well.