The paper reports on a qualitative case study of one high school library. It forms part of a broader study of the Bookery’s School Library Project which has established 40 libraries in disadvantaged schools in Cape Town. The paper examines what difference the library is making to the school. The overarching aim is to find what might be learned from the Bookery’s Library Assistant (LA) programme about the staffing of school libraries in the South African context, where fewer than 20% of schools have functional libraries. The case study over two weeks comprised observations, interviews, and a questionnaire survey of the teachers. The working relations between the Bookery library assistant and the “teacher-librarian”, a full- time class teacher and the library’s driving force, are found to be crucial to the library’s sustainability. The library is clearly playing an important role in the students’ school experience and in meeting the information needs of teachers in their classroom teaching. But, despite general beliefs that the library is “a good thing”, only a minority of teachers integrate it into their teaching. It seems that teachers lack insight into the role of a library and information literacy in 21st century learning. Other key restrictions on the fulfilment of the library’s potential are its limited collections and the lack of ICTs. In the words of one participant, the overall conclusion is that “ It is helping but there are limitations”.