Of course, on many levels, your DH is right. If we OTT on the Kumon, the tutors at Yr1 etc. our DC will burn out. Also, it doesn't matter how many degrees, or what class they are, that any DC may get, if they can't get on with people, then they are not going to get very far in the world outside school or beyond school.
But, today you often, very often, need more than just one degree to even get onto a professional course (eg you need a masters to get onto a building surveying course, or to become an educational psychologist). Then there are all the professional qualifications that follow on from that. I was beyond belief the other weekend at a family lunch when I discovered that my uncle who is retiring as a successful barrister, did not EVEN HAVE A DEGREE. Double !!
Plus, and this is pure conjecture on my part, but is how I feel about myself: I am a stay-at-home mum, out of choice, and I feel it's part of my "role" to keep an eye on my DC's education and to support them in it, particularly in view of this future competitive career-market that I've mentioned. It's part of my justification for staying at home and not supporting the family more financially (and we could always do with it!).
Finally, I would say, that I meet many more like-minded people here than I do at the school gate, so it's also a great support when I'm perplexed, worried, interested or just !