Fable
The wood the apprentice practices on every day
The carpenter's shop was to train a group of apprentices to make chairs. The old master picked out a pile of practice wood: softwood, hardwood, curved-grain wood, and a few bad pieces with hidden knots. The apprentices practiced on these samples every day and became more and more alike.
At first the results were good. The apprentices could all build a steady chair in the shop exam, so the master assumed they had learned the rules of chair-making. The walls were covered with passing work, and outsiders who saw it thought this batch of apprentices was ready to graduate.
The first out-of-town orders arrived, and so did trouble. Southern damp wood swells, northern dry wood cracks, inns want stackable chairs, and schools want low-legged chairs. The apprentice had only seen what was in the practice pile, and got confused when encountering new wood.
Someone suggested putting the good chairs used for exams into the practice pile too. Short-term scores were higher, but apprentices began memorizing the exam grain patterns, copying the approach whenever they saw similar wood grain. Scores looked good, but out-of-town repairs did not decrease.
The master reorganized the practice pile: which wood represented common orders, which represented rare but dangerous situations, and which could only be used for assessment and not shown to the apprentice in advance. Duplicate samples, dirty samples, and mislabeled samples all had to be removed, and missing scenarios had to be added.
He also recorded why each piece of wood was selected. If the practice pile came only from old customers, the apprentice would lean toward old models; if there was too little bad material, the apprentice would not learn to avoid risk; if the labels were wrong, the apprentice would mistake the wrong method for craftsmanship.
A few months later, apprentice exam scores did not skyrocket overnight, but out-of-town order rework decreased. The master understood: whichever pile of samples an apprentice learns from, that pile becomes their world. The boundary of the practice materials is the boundary of the capability.
Later, when new apprentices joined, the master would first take them to see the gaps in the practice pile. He said, don't assume that what's in the pile is the whole world, and don't assume that what's not in the pile won't happen. Real teaching begins with acknowledging that samples have boundaries. Later, the shop also kept a small pile of unfamiliar wood, brought out only when apprentices were about to graduate, to prevent them from memorizing only the grain patterns of the practice pile. If new orders started coming from elsewhere, the practice pile had to be updated accordingly.