The data arise from a sociological study
  of Australian Aboriginal and white children reported by
  Quine (1975).
  
In this study, children of both sexes from four age groups
  (final grade in primary schools and first, second and third form  
  in secondary school) and from two cultural groups were used.
  The children in age group were classified as slow or average 
  learners. The response variable was the number of days absent   
  from school during the school year. (Children who had suffered
  a serious illness during the years were excluded.)