Sentence:  Imagine a country where children do nothing but play until they start compulsory schooling at age seven. Then, without exception, they attend comprehensives until the age of 16. Charging school fees is illegal, and so is sorting <WSD>pupils</WSD> into ability groups by streaming or setting. 
Meaning of the word marked with <WSD> tags:  (student)A learner under the supervision of a teacher or professor.