Fable
The final acceptance check in the sealed exam papers
The county school prepared to select an arithmetic teacher. The education official first handed out a stack of practice papers; students did them daily, and mistakes were explained. After a few weeks, everyone's scores rose sharply, and the education official thought this was encouraging.
The teaching assistant reminded them that the practice sheets had already been memorized by the students, so they couldn't show whether the students could solve new problems. The instructor then took another stack of diagnostic papers, and each time he changed the explanation, he used them to see where things were still weak. After several rounds, the question types and lecture pace both smoothed out.
A certain teacher secretly also used the practice exam papers for lessons, and scores rose another notch. When a neighboring county came to exchange ideas, the questions were changed, and the students immediately revealed their weakness: they could recognize familiar faces, but could not handle unfamiliar accounts.
Only then did the old instructor lock the third wooden box, with a seal pasted on it, and no lecture, question revision, or seating arrangement was allowed to open it. Only when the teachers decided 'no more changes' would it be unsealed in public and the students allowed to take one final exam.
The new teacher very much wanted to look at the third wooden box in advance, on the grounds that he feared the students would suffer a loss. The old instructor refused: if the final assessment were also used for practice, the scores would look good, but the people selected might not be able to teach unfamiliar children how to keep accounts.
On the day of the exam, the seal was torn open in public. Some people hit every target on practice papers but panicked when they encountered new questions; others had mediocre adjusted test scores but could steadily solve unfamiliar accounts. Only then did the county school understand that the last box had preserved honest acceptance checks.
Sealing the exam papers also kept the instructor in check. Each time he revised his teaching approach, he could only look at changes in practice papers and tuning papers, not sneak a peek at the final wooden box. This was slower, but it prevented tuning the teaching to merely cater to the final set of questions. Later, when the county school published results, it also explained which papers were for practice, which for tuning, and which one was only opened at the end. Everyone finally understood that sealing wasn't mystification, but leaving a clean mirror for true ability. Scores thus lost their false heat.
The final exam score is not necessarily the prettiest, but it is closest to real ability. Practice papers are for learning, diagnostic papers are for improving teaching, and sealed papers are for estimating what will happen after leaving school. An exam paper seen in advance will lie no matter how accurate it is.