At what age should a teenage boy start shaving?

when he starts growing facial hair.At what age should a teenage boy start shaving?
Theres no real age for it, whenever your face gets enough hair thats a good indication that it's time to shave.At what age should a teenage boy start shaving?
any age if fine as when you get facial hiar, some kids did at 11 some at 14.
when he has something there to shave, i hate it when people leave the dirty stach for years.