According to Plato, how does he envision the ruling class in his ideal state being selected?

Plato, in his work "The Republic", envisions the ruling class in his ideal state to be selected through a rigorous process of education and testing. Here are the steps:

1. All children in the state, regardless of their social status, undergo the same basic education until they reach the age of 18. This education includes physical training, music, and basic mathematics.

2. At the age of 18, those who excel in their studies are selected for further education. This education focuses on advanced mathematics and includes a study of the five mathematical disciplines: arithmetic, plane geometry, solid geometry, astronomy, and harmonics.

3. At the age of 20, those who excel in their mathematical studies are selected for military and physical training. This training lasts for two years.

4. At the age of 30, those who excel in their military and physical training are selected for a higher level of education. This education focuses on dialectics and lasts for five years.

5. At the age of 35, those who excel in their dialectical studies are selected for practical training in ruling the state. This training lasts for 15 years.

6. At the age of 50, those who excel in their practical training and show a deep understanding of the Form of the Good are selected to be the rulers of the state. These rulers are known as philosopher-kings.

In this way, Plato envisions the ruling class in his ideal state to be selected based on merit and ability, rather than birth