Rome became a REPUBLIC at the end of the 6th Century BCE.
Explanation:
When Rome defeated the Etruscan conquerors, Rome became a republic in 6th century. In a republic state, the government is elected by the people itself. All males over the age of 15 who were direct descendants of the roman tribe became the citizens of Rome.
Since Rome became a republic, it was divided into three major parts. These parts go by the names of the Senate, the Consuls and the Assemblies. The Senate was considered high class as they composed of patricians, the noble and wealthy families.