This article is from the Martial Arts FAQ, by Matthew Weigel email@example.com with numerous contributions by others.
In general, yes. Some of the possible positives would be control of
agressiveness, instilling self-respect and self-control, as well as
The style that a child should take is a totally different question,
and is directly influenced by the style, if any, of the parents. It
will of course be convenient if the child can practice with, or at
least in the same school as, the parents. The major issue with
children in the martial arts is the integrity and trustworthiness of
the teacher and the school.
The joints and connective tissues of children are more vulnerable to
injury than those of adults. Keep this in mind when selecting a style
and school for a child, and discuss it with the instructor. Schools
which allow agressive joint locks to be applied to children or don't
train them to refrain from snapping/hyper-extending elbows on strikes
and knees on kicks should be avoided. (It is for this same reason
that good baseball coaches will not allow young pitchers to throw
pitches which require hard snapping of the arm - like curve balls).
Throws, however, are quite different; the small size of children makes
them naturals for arts which require falling down.