Most Demon Spawn die before they are even given a chance to be Selected.

A Teacher representing each Master collects the most promising ones and takes them to special Training areas.

The food and resources available for growth are still very limited at this point, but cannibalization is no longer allowed, as the spark of intelligence has begun to flicker. 

Those that cannot fight for food and space quickly perish.

From this group the remaining Demon Spawn are put through a rigorous series of physical tests. As they begin to understand the world around them, they are instructed on the basics of channeling their energy for both offense and defense.

These tests result in many more of each batch perishing.

The remaining Spawn are considered "true" Demons only after four years or so of physical tempering.

Instructions on Demonic Culture, Etiquette, Language, and History begin at this point. 

Some Demons never learn how to truly speak or reason but teaching them earlier is considered a waste of energy as the mortality rate is so high.

-Section from "The Path to Strength, Demonic growth from Spawn to Nobility; Fifth edition"