I think that the parents did wrong, but I also think that willful ignorance of your child's habits is just as wrong. Simply sending them to an abstinance-only sex ed and then blithely assuming that they're not going to have sex is naive at best.
I think it's naive that you think that's all we do.
I don't have any magic bullets that will keep a kid a virgin until his or her wedding night. Keeping a kid a virgin until she or he turns 16 is not really that difficult. Education, supervision, rules, expectations (high ones), and hands-on parenting is what it takes. Prayer is useful as well.
Thank you. A sane thought prevails.....