"You can see from the books here that it's an enormous job. It's huge but we have a nice little core team that work hard all year.
"It will be a very sad for it to end. It will be a very sombre occasion on Sunday afternoon, thanking our volunteers, because it's the same people every year. The same amazing people giving me their free time."
Book Sale Volunteer, Neill Gordon said lifting hundreds of boxes and giving up about 30 Saturdays a year was "hard yakka".
"It's a huge ask," he said. "It is a very virtuous circle. People are pleased to be donating books, thrilled to get them at bargain prices and the school makes some money into the bargain."
Clarke said the number of booksellers had fallen.
"From 10 years ago we would have had 12 to 15 travelling long distances to buy and now we have four or five that come through."
The sale will be held from 9am to 4pm this Saturday and 9am to noon on Sunday.
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