> Where are you more likely to find a mentor, in a school with 10 teachers or 200 teachers? Where are you more likely to find a friend, in a school with 50 or 5000 people?
This is such nonsense. Beyond a certain (very low) number, the number of people at the school doesn't help you with those things, because you can only meet so many people. You have classes with a fixed number of teachers, and a fixed number of students in each class. Furthermore, it's usually roughly the same cohort in each class. So even at a school of 5000 people, you only productively meet a small fraction anyways. Besides that, the premise is seemingly that a good school is one where you can find a maximally good mentor and friend. But schools are for teaching things, so ensuring you can find a slightly better mentor or friend at best marginally improves the school as a school. If the charter school is better than a public school in some other dimension, then that will surely overshadow this miniscule effect.
You've seemingly borrowed an argument for larger cities and applied it to schools without understanding it. If I am lacking something in a small town, I either put up with it, or move to another town where I will surely lack something else. If I lack something at a school, I have the choice to switch schools to one where I am better provided for (assuming I'm given that option) or find something to supplement that lack outside of school (say a club, sports team, etc).