An advertisement on television at the moment ends with: “It’s good to be a dad. It’s better to be a friend.” The premise is that perfect parenting can be achieved by simply acting the same age as your child, rounding off a day in the park with a fruit-flavoured drink. I’m no expert on parenting, but if Philip Larkin was right and they really do fuck you up, your mum and dad, the parent-as-friend technique seems a sure way of achieving that end.

Take Demi and her mother. Demi’s father had left them. Demi’s mother was clearly struggling as a single parent and needed someone to confide in. Demi became her best friend. When things were going well, they would go shopping together, get their hair and nails done, and Demi would accompany her mother on dates with various new men. Every time a boyfriend let her down, she would pour out her woes to her daughter, accompanied by a bitter diatribe against Demi’s father.

“I hate men. They’re all useless and unreliable,” Demi once told me during a guided reading session. This thought may have crossed my own mind occasionally, but to hear it from an eight-year-old was more than a little disturbing.

It soon emerged that man problems weren’t all that Demi’s mother shared with her. In a lesson on negative numbers, which introduced the concept of bank overdrafts, Demi appeared surprisingly well informed on the topic of debt. I overheard her telling other children what to do if the bailiffs came round.

I talked to the school’s pastoral care worker, who began to have regular sessions with Demi and paid several visits to her mother.

Then, one day, the principal called me into his office. Demi’s mother had taken an overdose. She had been up to her eyes in debt, had fallen out with her friends and had been dumped by her latest boyfriend. Demi’s grandparents had rushed her to hospital, where she was recovering.

I don’t know if Demi was ever told what had happened to her mother that day; it was nearly the summer holiday and in September she was no longer in my class. I know that her grandparents wanted her to live with them but Demi resisted fiercely: her mother needed looking after. While her classmates were worrying about stolen pencils, Demi was worrying about the bailiffs and how she could stop her mother crying. The traditional parent- child relationship had been reversed.

My own childhood could not have been further removed from Demi’s. Even though adults led dull lives, sitting still and chatting for hours without feeling the need to run around, I couldn’t wait to be one of them. Adults, unlike children, had no problems. They could eat biscuits from the tin without permission and go to bed as late as they liked. Their role in life was to be there for you, to ferry you around, tell you off, feed you and help to solve your problems.

Unlike Demi, I got years of childhood before I had to grow up. In all the time I’ve been teaching, I’ve never come across a parent who didn’t want the best for their child, but I’m pretty sure that being their friend is not the way to achieve it.

Jo Brighouse is a teacher at a school for children aged 4-11 in the Midlands, England. Ms Anne Thrope is away.