I had thought that the words pupil and student were more or less interchangeable. My feeling, maybe it was just a feeling? was that a pupil was someone who went to school, while a student was someone who studied. But, meaning more or less the same thing.
I recall joking while I was in high school that I was more of a pupil than a student, because I did, indeed, go to school, but I never actually studied.
It is possible that I was correct in the American sense of the terms. The English, however, seem to see more of a distinction, based on etymology. My Oxford Concise defines a pupil as "one who is taught by another," and a student as "one who studies at secondary or higher education." So there are elementary school pupils and high school and university students. This because pupil is based in words that describe children.
There would be a certain rhythm to that.
The question was posed to me directly by a Thai friend. They are full of questions like this. "What is the difference between a pupil and a student?"
The two equivalent words in Thai are used in a more clear cut manner. A "nak-rien" attends elementary school or high school, while a "nak-suksa" attends university. "Rien" is the verb meaning to study; "suksa" has the broader meaning of learning, which implies more understanding.
I really learn a lot when I consider these sincere, relevant questions. Thanks, guys!