I do think it would help if they also encouraged boys to remain chaste until marriage.
With my son when he began to date, I old him that he must treat every girl he dates the way he would expect boys would treat his little sister.
That worked well and when he was in his senior year of high school and had been dating a girl for almost a year, he confessed to me that both wanted to have sex and he was not sure he could meet the expectations I had encouraged.
At that point the lesson became, use protection, use protection, use protection even if she says she is on the pill.
My husband and I are encouraging both of our children (boy and girl) to remain chaste.