It is a discussion that can be fraught with embarrassment and misunderstanding.
So, when it comes to sex education, what are students' funniest or strangest questions?
On social media, teachers have revealed the comments from students that still haunt them – or make them chuckle – to this day.
Often, it is students' disbelief that their parents, or indeed teachers, "did the deed" that can provoke the most humour.
Cringeworthy moments in sex education lessons
Deputy headteacher Mr Grocutt kicked off the discussion, tweeting: "Best line I’ve had in a sex and relationships lesson today: ‘My dad did that?!’"
Best line I’ve had in a sex and relationships lesson today:— Mr G 🙋♂️ (@deputygrocott) November 12, 2020
‘My dad did that?!’
Other teachers commented that delivering a sex education lesson while pregnant prompted horrified glances from students as they joined the dots.
I did that lesson 8 months pregnant and 55 pairs of eyes starred in disbelief and slight disgust at me 👀 🤦♀️— Mrs Louise 💛🌻👂 (@MrsLouise4) November 12, 2020
Whilst working as a TA in a secondary school, I was in a science lesson when y8 boys were doing conception and birth. After watching a baby being born a boy asked if it hurt...teacher said: ask Miss - she’ll know...30 pairs of 13 year old boys eyes 👀😬😬 😳— Donna Burkert (@donsybee) November 12, 2020
I remember doing a RSE lesson when I was heavily pregnant and one student asking why I hadn't followed the contraception advice I was dishing out. My husband also worked at the school so when he came into the room, the realisation of it all made the go very quiet!— MJTeach (@JMHTeach) November 12, 2020
Of course, these lessons can also sometimes be somewhat too revealing about the private lives of students' parents.
In a discussion on pubic hair, one teacher reported that a child announced "my mum's got loads of that", an image they said they "struggled to shake".
There can also be confusion over exactly how interactive the lessons might be. One student asked: "Miss, when we do sex education, does someone come in to demonstrate?"
Most comical line for me: Miss, when we do sex education does someone come in to demonstrate? 😳— Louise 🍎 (@happyteachr) November 12, 2020
Many reported students' bemusement over flavoured condoms, with one suggesting they might be a handy snack in the event of being stood up.
"Why would you need a flavoured condom...??"— Chris Bowstead ❤🩺🌈🔬🧪🔭 #AortaKnowBetter (@BunsenLearner) November 12, 2020
"So you have something to eat if your date doesn't turn up...."
And there were some surprising questions about sexually transmitted infections, too.
Y9 had a collapsed timetable day on sex, STIs and contraception. Cue asking me in a History lesson the next day "Miss, can you get crabs in your eyebrows after a BJ?" I wasn't sure whether to be mortified or pleased that they thought I would be open to answering questions?!?— Amanda Sexton (@AJSLaw18) November 12, 2020
It is true that the more comfortable the teacher is leading the discussion, the bolder students will feel in asking for clarity.
But as the above comments prove, these lessons can also provide unintentional hilarity.