I think christians who contribute money to their church made the abstinence only policy happen even though only 15% of U.S. citizens want an abstinence-only form of sex education. This is the "Moral Majority" in action.
Abstinence and abstinence-only education: A review of U.S. policies...
From this paper:
The United States continues to lead the developed world in adolescent pregnancy rates. Over 800,000 adolescents become pregnant each
year, 80% of these pregnancies are unintended, and many of
these end in abortion. An estimated 18.9 million STIs
occurred in 2000 in the United States; almost half of these
in adolescents and young adults under 25. Long-term
sequelae of STIs can include infertility, tubal pregnancy,
fetal and infant demise, chronic pelvic pain, and cervical
cancer.
The children of adolescent mothers perform more poorly on indicators of health and social well-being than children of older mothers 7% of parents did not want sex education to be taught. Only 15% wanted an abstinence-only form of sex education.
Although federal AOE funding language requires teach-
ing that sexual activity outside of the context of marriage is
likely to have harmful psychological effects, there are no
scientific data suggesting that consensual sex between ado-
lescents is harmful.
Data from a recent nationwide poll of middle school and
high school parents found overwhelming support for sex
education in school; 90% believed it was very or somewhat
important that sex education be taught in school, whereas
7% of parents did not want sex education to be taught.
Only 15% wanted an abstinence-only form of sex education.
Parents thought it was appropriate to provide high school
and middle school youth with broad information on sexual
issues, including sexually transmitted infections (99%),
“how babies are made” (96%), waiting to have intercourse
until older (95%), how to make responsible sexual choices
based on individual values (91%), how to use and where to
get contraceptives (86%), abortion (85%), masturbation
(77%), homosexuality (73%), oral sex (72%), and that teens
can obtain birth control pills from clinics and doctors with-
out parents’ permission (71%) [30]. In these polls, most
parents and most adolescents do not see education that
stresses abstinence while also providing information about
contraception as a mixed message.
1999, one-quarter of sex education teachers said they were
prohibited from teaching about contraception.