'Saddlebacking' should be the term for the phenomenon of Christian teens engaging in unprotected anal sex in order to preserve their virginities. 'After attending the Purity Ball, Heather and Bill saddlebacked all night because she's saving herself for marriage.' Please, please adopt this definition!"(dedicated site)Of course the problem is the kids are right. The people who think they are wrong are confusing chastity (purity of soul) with virginity (purity of body). Augustine (De Virgin. viii) "virginity is continence whereby integrity of the flesh is vowed, consecrated and observed in honor of the Creator of both soul and flesh." In other words as long as the integrity of the flesh is maintained virginity is maintained. The church has a notion of "virgins in the flesh but not in the spirit" which is a violation of chastity, not a violation of virginity. (example Jerome's letters to Eustochium) and that IMHO is the correct status for kids that engage in non vaginal sex acts but have never engaged in vaginal penetration. They lack chastity but not virginity.
Now what's interesting is this is a rising phenomenon. While at some point I'll do my upcoming series "Sex and Fundamentalism" which discusses virginity pledges, it does appear these sorts of pledges cuts the age for first anal sex by several years (to below the level of first vaginal sex for kids whose parents are liberal about sex). So this is a big issue.
On a related topic some kids think they are virgins if they have had vaginal sex but not ejaculated. And again loss of virginity is loss of integrity of the flesh. Once penetration happens virginity is lost.