It actually begins earlier than Highland Twins, starting in Goes To It/War with the following sequence of points:
Quote:
There were no examination results to announce; but, as she said, there were a good many items of news personal to the school.
Quote:
Jeanne de Lachenais was not yet allowed to do any work, for she had had a bad time and was still far from strong. But, during the past week, she had insisted on mingling with her colleagues, and was trying to persuade the Head to let her set her own exam papers.
Quote:
Next week’s exam-week? Has anyone realised that?
Quote:
Then they separated, those who had collecting to do to see what they could garner; the others to draw together and discuss what kind of papers they would be likely to get in the coming Oxford Examination. Seven of the Fifth and Sixth were taking School Certificate, and there were eight Junior Certificate. The events of the past few days had put such things as exams out of their heads; but now realisation of the fact that the trial was almost on them came with a shock, and they talked eagerly. Hitherto, the school had taken no public exams.
Obviously the last quote suggests that earlier references to exams were only internal, but it does show clearly when the school changed to the British system.