The left has not only infiltrated schools, they have also infiltrated many churches.
How do we counter “mass” indoctrination? Not much left other than the choice we wish not to take.
This is a link to a PDF of a book about, in part, an individual involved in the effort to get communists into seminaries as sleepers. I only started reading it but even early on you can see an example of why communists in education can be very dangerous.