A used-book swap fair at the start of the year

When a child moves up a class, many parents struggle to buy guide books. Meanwhile older pupils' used books lie neglected at home. At the start of the school year, hold a one-day fair in an open space or a school room. Pupils bring used books in good condition, sorted by class, and anyone who needs one takes it free or in exchange. Record who took what in a notebook. You need a few tables, volunteers and the school's permission.