Has it declined as much as we would expect, given the decrease in religiosity in the US over that time period? I've only found data going back to 1995,[0] which shows relatively flat numbers for the past 15 years or so.
(And the amount of parents which are interested in their children attending private schools vs those who have access to and can afford them is an entirely different discussion.)
(And the amount of parents which are interested in their children attending private schools vs those who have access to and can afford them is an entirely different discussion.)
[0] https://nces.ed.gov/programs/digest/d23/tables/dt23_205.10.a...