The instilling of doctrine systems or pastiches of ideological, religious or political beliefs particularly in opposition to contrary creeds may result in intolerance and fanaticism; or in conformism and fear. It may sharpen international and political, religious or ideological conflict and encourage subversive activities and espionage. It may serve to strengthen dictatorship, government control, injustice, inequality and exploitation. Indoctrination techniques include the use of propaganda, brainwashing, censorship and other restrictions on freedom of expression and information, advertising, angled phrasing and contents of government and official information, with monopoly of the media. The most effective means of indoctrination are through parental influence and institutional education.
Tax aid to non-public schools in the USA is ostensibly to enhance parental choice in education. Since 90% of non-public schools are sectarian, they tend to hire only "religious correct" teachers and to use textbooks that reinforce the doctrines of the sect that runs the school. It is argued that a great many non-public schools engage in sectarian indoctrination to such an extent that they guarantee a homogeneous sectarian school body and faculty.
Some degree of indoctrination is inevitable in any education system, if only because learning has to start somewhere, time is too short for everybody to discover everything for themselves, and reason is not sufficient to establish in each person de novo the complex matrix of beliefs, values, and attitudes that make civilized life possible.