	A solid collection management policy is believed to help school librarians build a robust collection that meets the aims and purposes of a school library. There are also various things that could, to various degrees, prevent the achievement of these purposes and goals. One major hindrance to ideal practice, which preoccupies much of the literature, is self-censorship.
Self-censorship essentially involves the decision either not to purchase or to remove library material. Of course, selection and deselection are quite legitimate practices which also involve these decisions, which makes self-censorship easy to either overlook or to conflate with ordinary collection management. A clear distinction is necessary to avoid self-censorship becoming invisible, subsumed into a legitimate activity.
	The key difference is whether the intent is to include material, or to exclude (or restrict) it. Selection should ideally focus on the inclusion of material if, among other things, it fulfils curriculum requirements or students’ interests and needs. Material that meets these requirements can be selected. Self-censorship focuses on removing or never acquiring material if it has particular features, which might (among other things) be seen as somehow immoral or otherwise objectionable. Even if it fits the curriculum and students’ needs and interests, Material cannot be selected if it has these characteristics, even if it fits the curriculum and students’ needs and interests.
	It is also necessary to distinguish between self-censorship from the general concept of censorship. The key distinction is whether the impetus to remove the item originated from inside or outside the library. If an outside group, such as parents, community groups, or teachers (who do not have library responsibility) attempts to have an item removed, this could be regarded as censorship. It is only internal decisions, made by library staff on their own initiative – though they may feel pressured to exclude certain material because of the community’s and school administration’s views and preferences – that constitute self-censorship.
Definitions of self-censorship are not limited to selection and deselection, however. Hielsberg and Hunt and Wachsmann argued that labelling attempts to prejudice attitudes towards a work, and thus qualifies as or at least encourages self-censorship. Hunt and Wachsmann, in particular, were concerned that it might lead teachers or librarians to declare certain areas off-limit to certain age levels, or if content warnings were included, embarrass students into avoiding books about particular topics.
Self-censorship is understood to be widespread throughout school libraries, though evidence of this is mostly anecdotal, partly because it is believed that self-censorship is difficult to measure.Many believe it poses an ideological problem for school libraries and media centres, as it contradicts principle of intellectual freedom — as aspired to by organisations such as the Library and Information Association of New Zealand Aotearoa (LIANZA), demonstrated by their “Statement on Intellectual Freedom”. The National Library of New Zealand refers to this in its exemplar school library collection policy. Outside New Zealand, support of intellectual freedom in schools is advocated by the American Library Association and, jointly, the ASLA and ALIA.
