what age do boys voices break?

[christywhisty]

DS is 11 (12 in September) Teacher thinks his voice is breaking. She said was all over the place the other day when he was reading out load.
Have noticed it is a bit rough lately but put it down to allergies and he always had quite a deep voice anyway.
He is tall for his age at 5'2. Would have thought he was still a bit young for puberty, but don't really know much about boys as we only seem to have girls in the family.

14 is the typical age. I think it's very unusual under 13.

Ds1's voice has been broken for a while - he's 13, DS2 was 12 last week - not a hint.