(hopefully this is somewhat you are looking for or a place you can start at, have a nice day!)
Teenagers can avoid forming preconceptions about sex by educating themselves and not falling for fake media. Since a lot of teens are online and on social media now there is a lot of information going around, some of it true and some of it not. By staying educated, researching from many different reliable sources, and asking someone you trust teenagers can reduce the ability to form preconceptions.