high rate of teenage pregnancy

well i don't understand why is the rate of teenage pregnancy so high, students all over the world get the advantage of being taught about SEX, HIV and all other stuff but still today the rate is getting higher and higher, why have a child while your still a child.
you still need support from your parents and you know they are struggling but you still have unprotected sex and bring some one to the world

 sex under 18 is illegal in most states. It is statutory rape and punishable by prison. Contraceptives are also illegal if under 18 as well. Abstinence is taught more than anything else. Contraceptives are not free either you have to pay rands for them. . These girls all have to rely on their parents and family to support the babies