This paper presents additional information from the authors' 2009 survey of young people's reading and writing--for more information see their forthcoming report Clark and Douglas (2010) "Young People's Reading and Writing: An in-depth study focusing on enjoyment, behaviour, attitudes and attainment." To support the School Library Commission's evidence base, this paper explores what young people think about school libraries--do they use them? If yes, why? If not, why not? It also outlines how school library usage differs according to background demographics and reading attainment, and how it relates to wider enjoyment of reading, attitudes towards reading and reading frequency. This report has shown that most young people use the school library. They use it because it gives them easy access to books, because it is a friendly space and because they believe that the school library, and by default reading, will help them do better at school. The authors have also shown that their school library use is related to their ethnic background, age and gender. It also shows a link between school library use and increased reading enjoyment, higher self-assessments of reading ability as well as more positive attitudes towards reading. Most interestingly, there is a clear link between attainment and school library usage. Young people with a reading age above the expected level for their age are twice as likely to be school library users as their peers with a reading level below that expected for their age. The link is not necessarily causal, but it suggests that school libraries have a vital role to play in the reading patterns of those pupils who have higher literacy levels. (Contains 8 tables and 14 endnotes.)