Provision of textbooks to students can be constrained by school budgets, professional qualifications and levels of achievement of teachers and school administrators, and ideological influences. Inadequate budgets can lead, for example, to retention of dated, inaccurate accounts of history or expositions of the sciences. Lack of procedures to assure acquisition of the best possible texts can lead to the use of those that are pedagogically inferior. This also results from indiscriminate preference for authors of the some institutions, school systems or regions on the 'native son' principal, or for financial reasons; or conversely, the blind following of the leading text-book publishers, or university presses because of their expensive textbook promotion campaigns, or 'safe' reputation. Thirdly, ideological influences account for textbooks with racial bias, excessive nationalism, bias against theories in biology (such as evolution), cosmogenesis ('Big Bang' versus 'Continuous Creation'), or in psychology. Bias against socialism, communism, capitalism, militarism and other 'isms' are sometimes demanded by their respective opposite environments. All of the foregoing result in generations of ill-informed and, frequently, prejudiced citizens.