The pre-kindergarten class. This is the lowest level of class and it is the class before kindergarten class.
The class before first grade class. Generally for 5-year-olds, but sometimes includes 4-to-6-year-olds.
The class after Kindergarten. The first school year of primary education is referred to as First Grade of Primary.
The second grade forms the second layer of the foundation of a child's primary education. In the second grade, children are usually 7 to 8 years old.
Third grade (also called grade three or primary 3) is a year of primary education in many countries. It is the third school year of primary school. Students are usually 8–9 years old