This says that the average private highschool tuition is $15,645.
In 2003, the average private highschool tuition was $8,412 (Snyder, Dillow, & Hoffman, 2008), or $14,079 (in today's dollars).
Please correct me if I've made some mistake, but plugging those numbers in shows that the annualized real increase in price is 0.5% per year over 20 years. Looks like doing the same thing for public 4 year college over the same timespan results in an annual real increase in 2.1%
The first bullet says: “$23,839 is the average annual tuition among the nation’s private K-12 schools.”
Edit: it looks like there is an error on this page. The bar chart the numbers are much higher. Anecdotally, private high school is always more expensive than private elementary. That is what the bar chart shows but not the bullets.
Please correct me if I've made some mistake, but plugging those numbers in shows that the annualized real increase in price is 0.5% per year over 20 years. Looks like doing the same thing for public 4 year college over the same timespan results in an annual real increase in 2.1%