Chaos School was an educational institution under the Gray Temple. It consisted of two sections—primary section and secondary section. Children went to either of the two sections based on their age and skills.
Students between 5 to 12 years old were educated at the primary section. They would study rudimentary knowledge, common language, arithmetic, etc.
Meanwhile, their special talents and skills would also be developed there, like magic skills, observing skills, calculating skills… Prior to entering the secondary section, they would be tested first, and those who passed the test would gain the right to receive further education at the secondary section.
If they couldn't pass the test before they turned 12, they would be forced to leave the Chaos School. In fact, five out of six students would be expelled.