Turner Drury, age 13, of White Plains, N.Y., for his question:

WHAT IS A HYPERACTIVE CHILD?

A hyperactive child is one who has a disorder that causes him to be almost constantly active. Doctors call it hyperkinesis or hyperkinetic impulse disorder.

Most hyperactive youngsters can't concentrate on work assignments or games for long periods of time. As a result, they often fall behind in school. Doctors say that hyperkinesis can result from a physical disorder, such as a problem in the functioning of the brain. It can also result from social problems at school or in the home, or from a combination of physical and social difficulties.

Doctors sometimes prescribe tranquilizing drugs or sometimes they prescribe stimulants.

Special schools help lots of hyperactive children. Many also become calmer as they grow older.