It's grim but I'm now a veteran and I can only say that it's really not as bad as it seems.
For a start the numbers are misleading. Of those 400 for 40 places, many of them will be trying for multiple schools, anything up to 10. Secondly my older two are now in top 30 schools and neither of them are geniuses and nor are the vast majority of their friends.
My eldest completely flunked grammar exams and then got into two of the three independents he applied for, all of which were v selective as we stupidly didn't do a banker as we'd have rather gone state. His practice comprehension papers were abysmal, truly awful, and I remember saying to dh, 'oh well at least he's getting 75% in those maths papers you're marking' to which dh confessed that he wasn't getting anywhere near that he'd been fudging it so as not to demoralise him.
Oh and they have no musical talent nor particular sporting prowess, nor are they the sort of children that can chat about particle physics.
And another thing - one of them didn't have any head's references because the head was off sick and it was a chaotic state primary.
They are lovely though, obviously, and above averagely academic. As is your ds I'm sure. Don't believe that everyone else applying is some sort of hard working genius child with grade 8 violin and a cricket blue.