You're not allowed to do very much until you're 18.
You can't vote. You can't buy cigarettes or alcohol, serve on a jury, make a will, change your name, make a legal contract, place a bet or buy paint thinner.
(I'm not completely sure about this last one. But it's what our local DIY shop thinks.)
All you're meant to do as a teenager is go to school and work hard. Exam follows exam. You learn all the facts and then produce them to order.
"I promise you," I say to my daughter, who is coming up to yet more exams this summer, "it's not like this forever." She has dark circles under her eyes.
Last weekend I met up with a friend I hadn't seen for years. We got to know each other as teenagers. We used to take the same long bus ride to school and skive off games together.
On Sundays we'd take her dog for a walk. (There wasn't much else to do on Sundays in those days. Most people just fell asleep in front of the telly.)
The minute I saw her I started smiling, and I didn't stop all night.
She has two teenage boys of her own. She introduced me, saying, "We were at school together" and they looked at me with some anxiety as if, like an ancient Egyptian mummy, I might crumble away in front of their eyes.
My friend and I talked all night. We didn't stop. We told each other all the good and terrible things that had happened over the years. We laughed a lot. We are older, a bit more battered, but essentially the same.
And this is the strange thing about not being considered adult until you're 18. Sometimes, as a teenager, you don't make the best choices. You're more impulsive. You take risks. You flirt with danger.
But sometimes your judgement is perfect. You find people you like, and you still like them 20, 30, 40, 50 years later.
So you can read character and make lifelong commitments.
But you can't be trusted with a bottle of white spirit.
Which doesn't make a lot of sense, really.