NOT ALL PARENTS agree that "safe" promiscuous sex is superior to "risky sex" when it comes to disease and pregnancy. There are parents who would prefer their child get pregnant or have a baby even if not ready and possibly a premature marriage or relationship - that then might end in divorce or not - than to become promiscuous "semi-safely." Not everyone agrees that teen pregnancy is evil or wrong. Some do believe that sex SHOULD risk pregnancy - thus reducing promiscuity and all the dangers they see that as bringing. Some would rather their kid have sex once and get pregnant or have a baby, then have lots of sex, no kid, but then still risk being pregnancy from someone she had no relationship with at all and HIV positive too to her believing there is such a thing as "safe sex" with others who believe the same thing.
Who gets to gamble with their kid's whole life, future and values? The parents? Or the school?
In addition, the parents might not LIKE the condoms the school is giving out. For size. Quality. Whether or not has spermicide. Don't know how old they are. How they were stored etc.
The school handing out condoms is the school making a statement about sex - sex that may well be felony illegal to have - and that statement may exactly contradict the parents.