Spotted on our walk today.

This Harrison McGregor "Albion" Potato Digger was manufactured in Leigh, Lancashire early last century. It was devised around about 1870 to enable potatoes to be dug up mechanically rather than by hand using a fork. The device was drawn by a horse, then later by tractor. A blade is set to pass below the roots of the potato plants and the tines rotate to throw the spuds to the side so they could be gathered by hand. A seat would have been located on the bracket between the wheels, the driver operated the controls from there.
I spent a week each November in my school days, picking spuds for pocket money. The machines then were a little more sophisticated but used the same principle.
Historically school holidays were planned to fit in with the needs of agriculture, whether it was planting or harvesting crops.
For more detail see it large.