It all began with that which stands under and is understanding the Golden Egg that gave birth to all that is.
Kind of like a "Big Crack" that, unlike the Big Bang, includes a clue about the "But what happened before that?"

Science is needed!

which is why those asshats picked that particular age as the cutoff point.

Kids heading on to university can have their minds sullied by science. The rest need to be religiously orthodox and obedient little worker bees who will be too busy to learn much of anything but their jobs once they leave school.

It doesn't matter which gods they claim, religious nutters are all the same the world over, empowered by authoritarian men who get into power and then sit there forever, propped up by organized religion.

They'll go on to practice medicine and science for the upper castes and for us in the Western world, while their religion allows for the rest of their society to wallow at the bottom.