What makes it possible today is technology - dvds, satellite, internet, mp3 - and coops and retirees. As a youngster I always envied the kids at the local Catholic school. We knew they were ahead of us, and I hated it...;-)
Just like Moses wished that every Israelite would be a prophet, so I wish every Christian denomination had its own parochial schools. (And provided co-op support for their own homeschoolers.)