In automobile terms, the child supplies the power but the parents have to do the steering.
Source: First sentence of Baby and Child Care, quoted in Ladies' Home Journal, Mar 1960.
-- Benjamin Spock, (May 2 1903-1998), US physician, author; He was a major influence on modern U.S. child-rearing practices; Common Sense Book of Baby and Child Care, 1946 has sold millions of copies.