It doesn't have to be common. You can move to whatever school district you want to (if you have the money for housing there) and get that same level of education. No one's forcing you to send your kids to sub-par public schools.
Surely you don't believe the average American can just up and move to places with great public schools?
I was privileged enough to grow up someplace that allowed me to go to a great public school. It's a great city by many measures, but poor in public transport, affordable housing, and working-class jobs.
The OP has the means to home-school, so can live off a single income.
The OP has the means to pay their children nearly double the national average income (calculated on an hourly basis).
So, yes, in this case, the OP more than likely does have the means to move.
Or, the OP also has the means to be actively involved in the local schools and try to make them less awful.
My negative opinions on home-schoolers are based mostly on personal experience with home-schoolers in my area. They generally fall into one of two categories:
- fanatical Christians (public school is full of heathens and rapists etc)
- fanatical libertarians (I got mine, so fuck you)
Well yes, if you're only option is to send them to a sub-par public school then the government is going to force you to send them to that school. If you don't have the means to move to a better neighborhood, if you don't have the means to pay for private school you have to deal with what you get.
It does have to be "common" if 'you' (as in the OP) is claiming that "many" schools are excellent, with implicitly comparable graduation rates and destinations.
You should try raising a family in Southern California. See what kind of school district you can afford to live in. See if you still believe that "you can move to whatever school district you want to."