The case in three lines. The Seat, a river ledge where the whole town swims and fishes, is wearing out: the bank is crumbling, the litter is worse, and the trout are thinning. The council proposes a fence and paid permits. Ada asks whether the users made the rule, Casimir shows the town takes more fish than the river makes, Oriel shows a fine nobody checks is just a sign, and the anglers and swimmers draw up their own rules together. The councillor asks Tara which plan to choose, and the case stops there.

One question to ask. "What did Tara say?" Then: "What would make the users' plan fail?" There is a burning barbecue tray in the notebook; a good answer takes it seriously.

One thing to do at the table. Think of something your household shares and argues about: the television, the last biscuits, the hot water, the car. Who uses it, and when? Could the people who use it make a rule together that they would actually keep?

The grown-up layer. The case is about the commons. For years the "tragedy of the commons" story said shared resources must be either privatised or policed from above. Elinor Ostrom's Nobel-winning fieldwork found communities all over the world that had kept fisheries, forests and pastures going for generations by making their own rules, monitoring each other, keeping use within what the resource renews, and settling conflicts locally. It does not always work. The case deliberately leaves both plans with real costs, so that Tara's sentence has to weigh them.

The case leaves Tara's sentence blank on purpose. Ask for it before you offer yours.