Tamsin Oglesby must have been fun to be at school with. She once got into trouble for playing Tom Lehrer songs in class, which can’t have endeared her to her teachers. Now a playwright, her questioning mind and passion for fairness causes her to wrestle with many social issues and present them to her audiences for examination.

Her latest play, Future Conditional at London’s Old Vic, is a gem. After her children were turned down for her choice of secondary school, prompting obtuse battles with officials, she was determined to take the debate to the stage. For somebody who is not in the business, she has an astonishing grasp of the complex and murky world of Britain’s education system.

The play begins with parents chatting in the playground. They’re all friends until it’s time to send their children to secondary school - and then the cracks show. We meet the parent who wants everybody to send their child to the local secondary, until she’s offered a chance to send her offspring to a better school. We meet the parent who’s willing to pay, and the parent on benefits who hasn’t a chance.

Later, the parents argue fiercely and scrap with each other - something Oglesby says she has never witnessed, but which I can assure her does happen.

Then we meet Alia, an immigrant whose father was murdered in a Pakistani prison. She is a clear thinker, has a thirst for learning and takes every educational opportunity offered to her, but she is bewildered by the unfairness of our education system. Scenes with a government committee, whose brief is to look for “ways forward”, give Oglesby the opportunity to show the prejudice, deviousness and politicisation inherent in the education of our children. In one hilarious episode, the committee members behave just like the parents in the playground, pushing, shoving and insulting each other.

And then one member suggests bringing a child on to the committee. After all, shouldn’t they have a say in decisions affecting them? Alia is co-opted and her heartfelt and sensible plan for education is presented to the committee…if they care to consider it. “It’s not easy, growing flowers in the desert,” she says.

I found myself nodding furiously in agreement. Yes, this is how it is: the teacher being pressed by senior management to apologise to an appalling parent; the Oxford interviewers deciding whether to accept Alia or the boy who would make an excellent prop forward; the difficulties a teacher has in enthusing children. As a passionate believer in fairness for children, I was moved almost to tears by the final two scenes.

The young cast is outstanding, the musicians are terrific and Rob Brydon plays - with sympathy and understanding - the teacher we would all like for our children. And I have nothing but praise for Oglesby’s writing. Her aim, she says, was for us to emerge from the theatre talking passionately about education. We did, Tamsin, we did.