One obvious way to cut the cost of a holiday is to let schools set their own school year. There must be holidays at Xmas and Easter, but the summer holidays need not start at the end of July and carry on until the first week in September for EVERY school. If schools could set their own holidays, some summer holidays could start as early as late may, and some as late as mid August.
The result? Maybe an average of £1000 or more saved on a family holiday. Actually, everyone will benefit, even the single traveller and the airlines. The single traveller will pay less for their summer flights, and the airlines will benefit from an evening out of demand.