I wonder why they wait so long. Not that they follow the Bible, but the basis for doing it is biblical, and it is supposed to be done when the boy is a newborn.
When I was in Turkey in the summer of 1996, I saw whole families gathered on the grounds of the mosques, the "guest of honor", dressed in an elaborate costume, was the young man about to be trimmed
This is found in Genesis
17:23 And Abraham took Ishmael his son, and all that were born in his house, and all that were bought with his money, every male among the men of Abraham's house; and circumcised the flesh of their foreskin in the selfsame day, as God had said unto him.
17:24 And Abraham was ninety years old and nine, when he was circumcised in the flesh of his foreskin.
17:25 And Ishmael his son was thirteen years old, when he was circumcised in the flesh of his foreskin.
17:26 In the selfsame day was Abraham circumcised, and Ishmael his son.
17:27 And all the men of his house, born in the house, and bought with money of the stranger, were circumcised with him.