Like most healthcare professions, the education and certification of optometrists is regulated in most countries. Optometric professionals and optometry-related organizations interact with governmental agencies, other healthcare professionals, and the community to deliver eye- and vision-care.
The average length of an erect penis is 5.16 inches (13.12 centimeters) and the average circumference is 4.59 inches (11.66 centimeters), according to a new analysis of penis length studies involving more than 15,000 men around the world.
According to http://www.average-penis-size-chart.com/average-penis-length.html the average for a 13 year old is 3.5. The average between those two sites is about 3.75 so that's my guess. That is not my size, though. If the second website is correct, I have the size of a 24+ year old and I'm 13 (hate bragging.