Pupils should be taught how to say “no” to sex and learn how to deal with pressure from their classmates, according to a government-funded study. The London School of Hygiene and Tropical Medicine and University College London, which tracked 9,000 young people aged 13 to 21 across England, and more than 7,000 parents of teenagers aged 10 to 17 found that schools still focused too much on the biological side of sex.