Clifton, Habba and I just had a long, thread-dominating conversation about this, and I don't want to keep reiterating it and get in the way of posters on a new thread. But since you asked, I'll just point out that you, in your original post, framed the whole discussion of pushy parenting around the issue of Oxbridge and middle class professions:
"I've noticed a lot of people on mumsnet think that we are still in the 20th century and you can get to Oxbridge from a mediocre school without much effort. AIBU to think that the world is much more competitive now and there is no choice but to push DC to achieve?"
"DH is an Oxbridge graduate. He absolutely hates his job and quite unhappy about it (he works in finance). Yet it pays for a nice house in a nice location, kids schools, holidays, me being a SAHM."
You then went on to stress that you were very keen for your DCs to begin learning the violin at the age of three, because you believe that learning the violin (in particular) at this age is beneficial for brain development.
I then pointed out that a lot of the hype about no longer being in the "20th century" and the fear that you can't "get to Oxbridge from a mediocre school without much effort" is totally over the top - but drives a lot of pushy parenting, including the belief that extra curricular activities are very important for university/professional entry.
Of course lots of kids enjoy playing music. But getting worked up about Oxbridge and the 21st century when your DC is three is pretty over the top