According to the text, children are usually not physically ready to participate in organized sports until they are

The answer is "about 6 years old".

Before age 6 years, most kids don't have the fundamental aptitudes for sorted out games or sports. Equalization and capacity to focus are restricted, and vision and capacity to track moving articles are not completely develop. Rather, search for different games exercises that attention on fundamental abilities, for example, running, swimming, tumbling, tossing, and getting. 

The answer is metaphase