Proper upbringing, that's how.

I don't see how a 13 year-old wouldn't already know of such terms.

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I disagree.
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Take two saints for example, St. Maria Goretti and Jacinta Marto of Fatima.  I would call the latter "St.," but I don't want to start a flame war.
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Do you think they were "young adults" and not children? Do you think they knew all about hormones and concupiscence and "realtiy?" Do you think they heard it all from their friends or that their parents were "proactive?"
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Everyone who knew them testified they were unquestionably virgins, and never spoke a single word of impurity nor ever hinted at having any curiosity or interest in the topic. These were both childhood saints who directed the ENTIRETY of their will toward immediate and total rejection of any slightest inclination toward impurity, or sins of the flesh. They would not have the first thing to do with it, any more than St. Philomena would or the Blessed Virgin Mary herself would have.
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St. Maria Goretti suffered dozens of knife stabbing wounds from her assailant, Allesandro, who tried very hard to kill her when she firmly refused his impure advances. She was found bleeding to death, and was put on a horse-drawn wagon (which is very bumpy) and taken several miles that way (in agony) to get medical attention. The doctor speaking to her about her wounds heard her repeat that she only wished to forgive Allesandro. Does that sound like an adult with "proactive concupiscence?"
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My favorite example is the last days of Blessed Jacinta of Fatima. She had the opportunity to die peacefully and soon and was assured of going directly to heaven; or alternatively, to remain for yet a while on earth during which time she would suffer more for the remission of sins and for the Holy Father, who would have much to suffer. She didn't hesitate to choose the latter.
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Our Lady foretold she would therefore go to Lisbon and endure much pain, and would die alone without any other mortal present, but that Our Lady herself would be there to comfort her. That is exactly what happened. On the way, Dr. Castro Freire diagnosed her with "Purulent pleurisy with fistula, osteitis of the 7th and 8th ribs of the same side." If you don't know what that means, ask a nurse. Purulent is oozing pus. Pleurisy is a very painful infection of the flat cells of the pleura, the lining of the lung cavity. It makes breathing excruciating. Fistula is an open wound the size of a fist. Osteitis is bone infection, very painful, perhaps worse than pleurisy. Under all these conditions she would go into surgery without anesthesia. They didn't have an effective pain solution for her in those days. Yet knowing all this she was not afraid of the operation! She only had one fear.
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You would never guess what her one fear was, especially if you think that children ought to be proactively informed about sɛҳuąƖ sins.
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Her one and only fear was that during preparation for surgery, the exposure of her body to the hospital workers might be a near occasion for them to commit a mental sin of impurity in their hearts. Modern perverts will assure you that since there is no victim there is nothing wrong. But the something wrong is in the heart of the one who believes that, because the victim is one's own soul.
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Now, tell me that anyone knowing about her suffering willingly to OVERCOME in others the sin of entirely subjective impurity and appreciating her sacrifice to the point of willingness to imitate her heroic virtue, could ever bring himself to enjoy the illicit allurement of sinful impurity.
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St. Maria Goretti died offering her pains to the one who tried to kill her that way, and Blessed Jacinta died never having been accosted but nonetheless willingly offered her pains for the conversion of sinners, the reparation of sins committed against the Immaculate Heart of Mary and for the Holy Father because he would have much to suffer.
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These are models of virtue whose intentions we are well advised to remember, and strive to pursue ourselves.
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What draws my attention to the sermon is saying how far self-centredness is going today with the aid of new technology and the growth of substitution and simulation to replace or manipulate the natural order.

I disagree.
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Take two saints for example, St. Maria Goretti and Jacinta Marto of Fatima.  I would call the latter "St.," but I don't want to start a flame war.
.
Do you think they were "young adults" and not children? Do you think they knew all about hormones and concupiscence and "realtiy?"