The work of children was important in pre-industrial societies, as children needed to provide their labour for their survival and that of their group. Pre-industrial societies were characterised by low productivity and short life expectancy, preventing children from participating in productive work would be more harmful to their welfare and that of their group in the long run. In pre-industrial societies, there was little need for children to attend school. This is especially the case in non literate societies. Most pre-industrial skill and knowledge were amenable to being passed down through direct mentoring or apprenticing by competent adults.