How can you tell if a boy changes at puberty?

I'm not a boy but i wanted 2 c which boy in my class is already becoming a man? How can you tell if a boy changes at puberty?
Answer:
Their voice would be deeper or they'd sound like they have phlegm in their throat because they're voice is changing. They'll get a growth spurt too. They'll also get pimples and mood swings. Or you could look up "puberty" on wikipedia.

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all i know is that they have a growth spirt and their voice cracks

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Their voices squeak and get lower. They get taller. They get hair on their armpits and below the belt. They usually get acne. Their muscles get more developed.

And so on.

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They become taller, their voice may crack at times, and in some cases body hair, not alot, but in sparse amounts.

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