Is it possible that the 10 yr old in your class is homeschooled precisely because she's struggling to read?
Is it helpful to someone who struggles to read to presume to diagnose a cause attributable to the parents? Who do you attribute it to when you have a public school kid who can't read?
If we were to focus only on literacy, I think you'd find homeschoolers in aggregate do better than public schools.
But if socialization is the point, isn't it time we quit pretending that school is about anything else? (John Taylor Gatto comes to mind.) It's not like teaching 30 kids of the same age but vastly different aptitudes and interests is inherently more effective than teaching five of different ages who you know well.