Just to add, I found this which shows how careful one has to be with interpreting the data.
The 1861 census had a similar question on schooling asking whether children had been scholars attending school in the week prior to the census. It was meant to 'elicit the number of the population of those ages receiving instruction' .The report on the Scottish census said that the question had been useless for three reasons.
1) It excluded all children who were off school for ill health that week (and I'd note that quite often whole schools closed down for outbreaks of measles, scarlatina, cholera etc)
2) It excluded all children receiving education at home through tutors and governesses
3) The census for that year was held in Scotland on 7th April. It excluded many children in rural areas in Scotland as in many such areas schools were shut down for the whole of April ' to allow children to aid in the Spring agricultural operations'
Info from this very useful book
Drake, Michael, Ruth H Finnegan, and Jacqueline Eustace, Sources And Methods For Family And Community Historians (Cambridge: Cambridge University Press in association with the Open University, 1997), p. 26