Sex education is a highly controversial topic in traditional Indian society.
In a Delhi classroom, 40 sheepish girls and boys stare silently at a sketch of a couple making love.
The sex education lesson for 15-year-olds is not part of India's national syllabus, and the exclusive private school teaching the subject is taking a risk by passing on the facts of life to its pupils.
Traditionalists say such classes are against Hindu sensibilities and invade a private matter that is best dealt with inside the family home.
But, with rapid social change in India, calls for teenagers to be taught about human reproduction and sexual health are growing, and private schools across the country now give discreet lessons to their privileged pupils.
"India allows teenagers to learn English and other European languages, devour pizza, burgers, wear skimpy clothes, and dance to English music," teacher Rubina Hussain Sheikh told her class.
"These Western influences are welcomed. So why is talking about sex in schools not accepted?"
Sheikh, a counsellor whose lesson communicates sexual information in a simple and relaxed manner, admits it is a "tricky subject", but she believes it is a vital duty to combat ignorance.
She displays slides from the ancient Indian erotic text Kamasutra, as well as drawings of how an adolescent's body develops, and graphics to explain AIDS and the rise of sexually-transmitted diseases in India.
Students at the school often hesitate to ask questions, she said, but they all feel the course helps clear away many of the misconceptions and the secrecy that shrouds such taboo subject.