1920:

Teacher: "You should not engage in premarital sex, it can lead to pregnancy and disease"

1930:

Teacher: "You should not engage in premarital sex, it can lead to pregnancy and disease"

1940:

Teacher: "You should not engage in premarital sex, it can lead to pregnancy and disease"

1950:

Teacher: "You should not engage in premarital sex, it can lead to pregnancy and disease"

1960:

Teacher: "Boys and Girls, You are descended from apes. You cannot control your urges. It feels really good too."

1970:

Teacher: "Free Love, Sex is a Trip, Love the One You're With."

1980:

Teacher: "Just Do it!"

1990:

Teacher: "Boys and Girls, You are descended from apes. You cannot control your urges. Here are some condoms and a copy of the Kama Suttra"

2000:

Teacher: "Billy, you were wonderful! You know I love you, but don't tell the other kids because they might start rumors about us."