The awareness of sex in children starts innocently enough. The questions they ask at an early age can be dealt with simply enough. It is as they reach adolescence that their problems grow and the questions that they then ask are more difficult - the answers more likely to become a matter of controversy. The battle for sex education in schools has, for 30 years or more, nearly always been a matter of fierce controversy and debate. A recent film made by Dr Martin Cole became the subject of a national row. He appears in tonight's Man Alive with adolescents, parents, teachers and educationalists who come together to debate just how much children need to know; should be told; by whom; and at what age.