Let’s be clear: The Netherlands is a global leader. Dutch students consistently report lower rates of teen pregnancy and higher rates of contraceptive use than their peers in the US or UK. The philosophy of voorlichting is based on normalization—talking about bodies, desire, and boundaries with the same ease as discussing homework or soccer practice.
For specific resources from 1991 or similar, you might need to look into archives of health education programs, libraries, or historical collections of educational materials. Modern resources, however, can also provide comprehensive and age-appropriate information: Let’s be clear: The Netherlands is a global leader