Most teens become sexually active between ages 16-17. Sex education in public schools is optional and many teens are embarrassed to take the class. There are five categories of STDs - bacterial, fungal, viral, parasites, and protozoal - which can be transmitted through bodily fluids and some stay with a person for life. Common STDs include chlamydia, gonorrhea, hepatitis B, herpes, and HPV. While contraceptives can prevent pregnancy, condoms are the most effective at around 94% in preventing STDs if used correctly and consistently. Abstinence is the only 100% effective way to prevent STDs.