As any parent who has been to his child's classroom or sporting activity knows, kids come in all sizes.

These size differences get pronounced when puberty arrives in some of the children and not others.

One of the more noticeable things that occur is that girls shoot up past the boys around 11 or 12 years of age. Then the boys catch up and pass them by around 14 or so.

This is the usual pattern, but many children follow their own pattern that can be very different from this.

Early and late bloomers are considered different from the normal pattern of puberty, but these patterns occur frequently in adolescents and should be considered a variant of normal. Both tend to run in the family with both boys and girls going into puberty a little later or earlier than their peers.

When should a parent worry?