Talking about sex can be embarrassing for parents and children.
'Circle time' discussions - one way schools approach the issue
Evidence suggests most young people would like to be able to talk openly with their parents about sex but apart from embarrassment, fears about being told off if they are doing something their parents disapprove of puts them off.
Step forward the sex education teacher, holding aloft a variety of condoms to be examined by a group of pupils.
"From experience, I know that only a few parents talk about sex with their children," said Danielle John, the health care co-ordinator and school counsellor at Lordswood Girls School in the leafy Harborne area of Birmingham.
"In the early stages of their lessons some pupils will find the need to show off to their peers, others will giggle with embarrassment."
Ms John said she initially establishes a ground rule with her pupils before these classes.
"I like to give them the 'right to pass', so if at any time they feel embarrassed or for any other reason did not wish to contribute they may say "pass".
Even though sex education comes under the aegis of personal, social and health education (PSHE) and is part of the national curriculum, it is not compulsory in all schools.
From a teacher's point of view, pupils have to be informed, to be empowered to make right decisions, to protect themselves and to learn to cope with relationships.
The knock-on effect should be a reduction of teenage pregnancies and sexually transmitted infections (STIs).
Schools say teaching adolescents issues surrounding sex has to include a variety of methods. They need to be presented with clear facts but most of all they must be given the opportunity to have a say in what is taught.
Children do not really want to learn about sex from books and worksheets.
"They want direct and honest answers to all their questions," said Ms John.
"Such methods as 'circle time' open debates, role-plays, asking questions anonymously, listening to and interviewing health visitors or sex education speakers."
Research conducted by the Schools Health Education Unit in Exeter, Devon, said children were increasingly relying on their school and less on their parents for their sex education.
"The majority still shy away from real issues," said Ms John. "Some parents have told me they preferred schools to be in charge of sex education."
However, Ms John said other parents had asked for their children to be exempted from her classes.
"A child who is withdrawn from education is a problem but we respect parents' wishes."
So, how can parents go about teaching their children the fundamentals of sex?
"Communicate, communicate, communicate!" advised Gordon Tillman, the assistant head teacher at Maidstone Girls Grammar School in Kent.
"Communicate through discussion and by providing objective and relevant information at appropriate times.
"Tackle issues as they arise, not always missing opportunities by putting communication off for another day."
Clare Smith, healthier school partnership co-ordinator for Southwark, Lambeth and Lewisham - London boroughs that have the highest teenage pregnancy rates in the country - urged parents to tell the truth when their children asked them questions.
"Children know when you are trying to fob them off. Listen to what your child is telling you. Don't assume you child has done something if they ask you about it."
Ms Smith said parents should start these discussions at an early stage of their children's development - physically, emotionally and intellectually.
"Start young and don't be embarrassed - children are only embarrassed about discussing these issues as they pick up parent and carer sensitivity on the subject. Get information from health, schools and faith groups to support you.
"Use things around that children see and are used to - don't hide things.
"For example, when watching TV or visiting a zoo, if animals are mating and a child asks what they are doing, tell them the truth - they probably know anyway.
"Remember that informing children about sex does not take away their natural innocence. They can still be children and explore their own sensitivities et cetera, whilst also having information about sex.
"Think about what information or advice you would have liked to have before you first had sex."