The SE programmes studied vary widely in terms of their scope (abstinence-only vs. comprehensive), position in the school curriculum (mandatory vs. optional, and integrated vs. stand-alone), duration (from a few months to several years), their age (from just starting to 20 years old), and several other characteristics. The cost per student reached is highly dependent on the developmental stage of programmes. Because teacher salaries are the most important cost component, the cost per student highly depends on the programme duration, class size, and teacher salary level. Other important cost components are operational, teaching materials, M&E, and advocacy, which may be costly in a context of low acceptance of SE. Through scaling-up and increased coverage the cost per student reached can be reduced significantly.