School is back in session and so is "sex education," as Netflix's hit teen drama returns for a fourth season that concludes the story of the Moondale gang.

However, they are no longer in Moondale. Otis (Asa Butterfield) and Eric (Nukuchi Gatwa) are faced with a new situation: their first day at Cavendish Sixth Form College. Otis is nervous about starting up a new clinic, and Eric prays not to be a loser again. But Cavendish is a culture shock for all of the students at Moondale, and they learn that the college has yoga in the communal garden, a strong sustainable atmosphere, and kids who are popular for their kindness!

Meanwhile in America, Maeve (Emma McKee) is living the dream while being taught by cult author Thomas Molloy (Dan Levy) at prestigious Wallace University. Otis misses her, but is adjusting to not being the only child at home and the only therapist on campus.

Here's what you need to know about "Sex Education" Season 4 on Netflix. Scroll down for trailers, cast information, etc.

"Sex Education" Season 4 is available on Netflix beginning Thursday, September 21 at 3 a.m. ET.

All eight episodes are available simultaneously.

The trailer for Season 4 of Sex Education begins with the dilemma of sending nudes. Otis receives one from Maeve, but is chagrined when she urges him to respond. From there, the trailer offers a glimpse into the very different world of Cavendish College.

The cast of Sex Education Season 4 is led by Asa Butterfield as Otis Milburn, a teen who opens a sex clinic at the school.

Gillian Anderson plays Jean Milburn, a renowned sex therapist and Otis' mother.

Other key cast members for "Sex Education" include:

"Sex Education" adds several new cast members. Most notably, Dan Levy ("Shits Creek") will appear as writer and professor Thomas Molloy.

Sadia Graham, Lisa McGillis, Marie Reuter, Jodi Turner Smith, Eshaan Akbar, Felix Mufti, Anthony Rexa, Alexandra James, Reda Elazwar, Bella McLean, and Imani Yashua also have new will also appear in the film.