A 15-year-old girl at a city academy in London has revealed how she smokes cannabis before school and used to drink whisky during lessons.
Research this week suggests that Natalie Mitchell's experiences with drink and drugs are typical for hundreds of teenagers.
The pupil, who lives in Hackney, east London, told The TES that she now smokes cannabis before school less often than in the past, only once every three weeks.
"It makes me think a bit more about my work, makes me concentrate more," she said. "I'm more chilled and less loud in class."
Her behaviour and attendance have improved significantly since last year, when she used to go on drinking binges on school nights, downing cider, brandy, vodka and Bacardi Breezers with a 17-year-old friend.
The teenager claims she never suffered hangovers but would often arrive at lessons tired and would occasionally fall asleep.
She would even bring alcohol into school on Fridays to give herself a "head start" for the weekend's heavy drinking.
"It was only in the last lesson, after three o'clock," she said. "It would be JD (Jack Daniel's bourbon) in a coke bottle. I would just have a little drop, then more later."
Natalie is one of 10 young people who agreed to be followed by a camera crew as part of a Channel 4 documentary on modern teenage life.
As part of their research, the producers surveyed more than 1,000 14 to 19-year-olds.
They found that more than half had come across people selling cannabis and alcohol in their school. Around 70 per cent said they regularly smoked cannabis and had seen pupils drinking in school grounds.
In addition, at least 60 of those surveyed said they had a friend who had lost their virginity at school.
Heather Rabbatts, managing director of 4Learning, Channel 4's education department, said the research showed that the rebellious teens of previous generations were being replaced by "teen adults" or "child carers".
The teenagers were often hedonistic, she said, but many had weighty responsibilities caring for family members, partly as a result of divorce and absent fathers.
This Teen Life broadcasts on Channel 4 on September 23