The “old school” in your question isn’t one single building or program disappearing, but a whole style of sex education that has been steadily replaced over the last century.

What “old school” sex education looked like

For most of the 20th century, sex ed in schools was:

  • Very limited and vague, often just basic biology or reproduction with little real-life context.
  • Centered on morality and fear: premarital sex was condemned; the goal was to prevent “immorality,” pregnancy, and STIs, not to help young people navigate relationships.
  • Often taught indirectly, via animals and plants (e.g., rabbit reproduction, flower pollination) instead of frank discussion of human sexuality.
  • Strongly influenced by religious and social norms, including racist, sexist, and classist assumptions about who needed to be “controlled.”

In the US, early programs around the 1910s–1920s framed sex ed as part of public health and “social hygiene,” especially around STIs. Chicago’s 1913 attempt at formal school sex ed, for example, was shut down after backlash, and the superintendent was forced to resign.

How and why that “old school” model faded

The old approach didn’t vanish overnight; it was chipped away by big social changes.

Key shifts:

  1. Post‑war and 1960s–70s social change
    • The sexual revolution and women’s rights movements pushed for more honest information about contraception, pregnancy, and consent.
 * Biology textbooks started including more detailed human reproductive content, not just plants and animals.
  1. Public health crises (STIs and HIV/AIDS)
    • Rising concern over sexually transmitted infections during and after the world wars, and later the HIV/AIDS epidemic, made “don’t talk about sex” look dangerously unrealistic.
 * Governments and medical groups began to support more structured sex ed to reduce disease and unintended pregnancy.
  1. Push toward “comprehensive” sex ed
    • By the late 20th century, many systems began moving away from pure abstinence messaging toward broader coverage: contraception, sexual orientation, consent, and healthy relationships.
 * In places like England, sex education was formally integrated into the curriculum by the 1980s and then further updated in the 21st century.
  1. Digital age pressures
    • With internet access, young people started learning about sex from porn, social media, and peers, making it obvious that minimal, moralizing “plumbing-only” lessons weren’t enough.
 * Modern discussions emphasize skills like communication, navigating pressure, and understanding identity—things old-school programs largely ignored.

So “what happened” is that the original, moralistic, euphemistic model has been steadily replaced (though unevenly and incompletely) by more explicit, health- and rights-oriented approaches in many places.

But the old style isn’t totally gone

Even today, you still see the legacy of that older model:

  • Some regions still mandate abstinence-only or strongly abstinence-focused curricula.
  • Community and political fights over “too explicit” content echo the same arguments that shut down early 1910s programs.
  • Many students report getting either almost no sex ed or still-awkward, incomplete lessons, then filling in the gaps online.

In other words, the old school philosophy —control, silence, and fear—remains in pockets, even as policy and research increasingly support more comprehensive, realistic teaching.

Quick forum-style takeaway

If you imagine your grandparents’ or great‑grandparents’ sex ed, it was:

  • Brief, moralizing, and often just “don’t do it.”
  • Deeply shaped by religion and social control, including discriminatory ideas.
  • Eventually undermined by social change, public health needs, and the internet, leading to the more open (but still very inconsistent) approaches we argue about today.

So the “old school” didn’t just vanish in a single moment—it’s been slowly remodelled, one policy fight, health crisis, and cultural shift at a time.

TL;DR: The old school of sex education—vague, moralistic, abstinence‑focused, and often discriminatory—was gradually replaced by more comprehensive, health-centered approaches driven by social change and public health pressures, but traces of that old model still shape many classrooms today.

Information gathered from public forums or data available on the internet and portrayed here.