Schools that charge under $15k/yr are mostly low-quality religious schools, with a few rare gems (mostly from the Catholics)
Full tuition at schools that people mean when they talk about how good private schools are, starts around $40k on the coasts (day rates, not boarding), and $18-20k at lesser-but-still-sometimes-decent schools in less-affluent areas.
[EDIT] Of course, per-pupil spending and tuition aren't entirely connected—on the one hand, many students don't pay the full rate (much like with private colleges) but on the other, the better private schools usually have other sources of funding of various sorts. Endowments, scholarship funds, lots of supplemental and sometimes quite-large donations from parents and alumni for various purposes.
Schools that charge under $15k/yr are mostly low-quality religious schools, with a few rare gems (mostly from the Catholics)
Full tuition at schools that people mean when they talk about how good private schools are, starts around $40k on the coasts (day rates, not boarding), and $18-20k at lesser-but-still-sometimes-decent schools in less-affluent areas.
[EDIT] Of course, per-pupil spending and tuition aren't entirely connected—on the one hand, many students don't pay the full rate (much like with private colleges) but on the other, the better private schools usually have other sources of funding of various sorts. Endowments, scholarship funds, lots of supplemental and sometimes quite-large donations from parents and alumni for various purposes.