I am assuming you are asking about sexual intercourse.
In prior years, particularly High School years, the topic isn't talked about a whole lot. Students usually leave with the anatomy of pleasure parts instead of the knowledge of how to pleasure their partner.
Watching adult videos online is most likely unrealistic. Some people don't realize that in those videos, those adults are professionals and not everyone acts like the way they do in bed.
Some students may find the topic hard to talk about. We are told of unrealistic beauty standards at a young age, and eventually how our parts are "supposed" look like. They are also fed very little about the information on how you can achieve climax; some people do things differently.
Growing up, students might experience times where they are hinted that sexual intercourse is shameful. Most students, therefore, feel discouraged to ask questions.
The topic of same-sex intercourse is also quite untouched. Negative stigma is often floating around constantly and would make students interested in the same sex to be discouraged to talk to others about the topic. They, therefore, often reserve to online adult videos which gives them the perception of unrealistic standards.
