Can't they see there is no embarrassment involved in answering three-, four- or five-year-olds' questions about their bodies in a way appropriate to their understanding, then building on this basis as issues arise?
To leave sex education until the age of nine, ten or 11 is too late for it to be a natural part of learning; it then becomes contrived. Children must be empowered to have control over their own bodies. Accurate information, discussed in a relaxed way, is an essential factor. Parents who avoid this responsibility put their children at risk - and that is no laughing matter nowadays.