Page 65. That was the page the girls whispered to one another in the last year of primary school as we passed the dog-eared copy of Forever around under the desks.
It's the cringe-inducing bit where Katherine meets Ralph for the first time. And yes, you remembered right - Ralph's a penis. Literally.
Katherine, a senior in high school, asks, quite understandably: "Does every penis have a name?"
"I can only speak for my own," Ralph's owner, Michael, replies.
And things get quite heated after that.
This is a frank story about losing your virginity in your first relationship. Par for the course in today's teenage novels, but when we were young, it was unbelievably shocking.
When it came to page 89, when Katherine and Michael have sex for the first time, it was almost too embarrassing a text for a giggly 10-year-old girl to carry on reading and I remember us collapsing with hysterical laughter.
Perhaps our age on reading it was why it was so very shocking to us - this was the sex education book, the first description of lovemaking that girls of a generation read.
It's actually about an 18-year-old girl, but we read it aged 10-12, years before any of us had even kissed a boy. By the time we were 18, we would probably have considered it completely adolescent.
Reading it now, I realise I barely noticed whole sections of it as a young reader. The part where Michael teaches Katherine to ski, for instance - I don't think we even bothered to read that bit. And I don't think we cared much about the story of Katherine realising there are more fish in the sea.
Meanwhile other iconic elements of the book - Sharon and Ike's rug, for instance, on which the lovemaking takes place - and the dedication to 'Randy' - bring back instant recognition. Of course, Randy was Judy Blume's daughter, but we didn't know that when we read it and it sounded hilarious. A world away from an English primary school in 1989.
Forever is graphically educational and compulsively readable, but it's tasteful and sensible, promoting safe sex. It's a 1970s American time capsule in its description of 'sheaths' and 'VD', and it seems so innocent, in fact, by modern teenage standards.
In the current edition there's a note from Blume stressing that today, the need to protect against STDs, 'especially AIDS', would have featured, and exhorting readers to 'take responsibility' if they become sexually active.
Interestingly (and I wonder if it was deliberate) Katherine doesn't experience a shred of teenage angst. This is not an introspective book; there are no worries about 'does he love me?' or 'are my thighs too fat?' The heroine is a super-confident young woman and her first love and first break-up are like water off a duck's back. It's not the teenage experience most of us remember, but Katherine is meant to be a role model, I suppose.
The 1975 novel caused a scandal at the time and has long been the target of censorship. Like many enduring children's authors, Judy Blume refused to patronise young readers and, instead, told the truth with groundbreaking frankness - it's easy to see why she's still so popular today.
Oh, and a final 'did you know?' Forever has been blamed for a decline in the popularity of the name Ralph.
Forever by Judy Blume is published by Pan Macmillan (£5.99)
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